University of Ghana http://ugspace.ug.edu.gh
EVALUATION OF FIVE VARIETIES OF ONION (Allium cepa L.) IN TWO 
DIFFERENT SAVANNAH ECOZONES IN GHANA 
 
 
BY 
 
MOHAMED ATTA 
(10586332) 
 
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN 
PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF MPHIL 
CROP SCIENCE DEGREE (AGRONOMY) 
 
CROP SCIENCE DEPARTMENT 
UNIVERSITY OF GHANA 
LEGON 
 
JULY, 2018
 
 
University of Ghana http://ugspace.ug.edu.gh
DECLARATION 
I, Mohamed Atta, author of this thesis do hereby declare that except for the references to other 
peoples’ work which have been duly cited, this thesis is the result of my own findings under the 
supervision of Professor G.O. Nkansah and Doctor (Mrs) C. Amoatey. I also declare that the work 
has neither in whole or part been presented for another degree in the University of Ghana or 
elsewhere. 
 
……………………………….. …...…..………………………….. 
                                                                             
Mohamed Atta Prof. G.O. Nkansah 
                                                                                                       
(Student) (Principal Supervisor) 
                                                                                                             
  
……………………………..… ………….……………………..… 
   
 (Date)  (Date) 
                                                        
  
   
 
   
  
  ……………… …………..…  ……………………………..… 
  
 Dr. (Mrs) C . Amoatey Dr. V. Y. Eziah  
 
(Co-sup ervisor) 
     (Head of Department) 
     
 ……………………..………… ...…………………………..… 
  
  (Date)  (Date) 
  
   
  
  
i 
   
  
  
University of Ghana http://ugspace.ug.edu.gh
DEDICATION 
‘THE KEY TO SUCCESS IS HARDWORK’ 
I therefore dedicate this work to my family especially my brother YAHYA KASSIM ATTA, 
Director of Kas Estate, Ghana Ltd, for their sacrifice towards my education and this work.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ii 
 
University of Ghana http://ugspace.ug.edu.gh
ACKNOWLEDGEMENT 
The preparation and submission of this thesis would not have been possible without the advice and 
support of some personalities whom I am indebted to. 
 
I would like to sincerely thank my supervisors, Prof. G.O. Nkansah, Director of Institute of Applied 
Science and Technology (IAST) of University of Ghana, Legon and Dr. (Mrs) C. Amoatey, Senior 
lecture of Crop Science Department, University of Ghana, Legon, for the constant advice and 
attention they have given me, and for their wealth of knowledge that they have freely shared on a 
daily basis. May ALLAH the almighty protect them and their families and give them long life and 
strength to continue with their good work. 
 
I am extremely grateful to all staff of Institute of Applied Science and Technology (IAST) of 
University of Ghana, Legon, especially Bukari Musah for their immense support during the study. 
 
I am equally grateful to Cephas Ametefe-Tsetse from Sogakope and Mac Kluvi Dogbey from 
Denu. My thanks also go to all the staff and workers of University of Ghana, Legon Research Farm 
especially Mr Nicholas Adjekum, Manager of UG-Research Farm for their support. 
 
I am most grateful to all my course mates especially Mr. Joseph Ampah not forgetting Mr. William 
A. Asante of the Crop Science Dept. of University of Ghana, Legon for support in data analysis.  
 
Finally, I express my profound gratitude to the Almighty ALLAH, for the strength and knowledge 
He provided me throughout my studies. AMEN 
iii 
 
University of Ghana http://ugspace.ug.edu.gh
ABSTRACT 
Two separate field experiments were conducted at Sogakope (Tordome), in the South-Tongu 
District of the Volta Region and at the University of Ghana Research farm, Legon, in the Greater 
Accra Region from August, 2017 to March, 2018. The aim of this study was to evaluate the yield 
performance of four introduced varieties of onion namely, Dayo, Trophy, Red-Creole, and Orient 
against the commonly grown variety ‘Bawku-Red’ under two different ecozones in Ghana. The 
experimental design used was a randomized complete block design (RCBD) with five (5) 
treatments and four (4) replications. The varieties represented the treatments. The data collected 
was subjected to analysis of variance (ANOVA) using GenStat 9th Edition Software. Means which 
differed significantly were compared using the Fisher’s Protected Least Significance Difference 
(LSD) at probability level of 5% of significance (P=0.05). Correlations analysis were done to 
determine the associations among parameters.  
 
The results showed that variety “Orient” performed better than the other varieties followed by 
“Trophy” in terms of vegetative growth, reproductive growth, bulb quality and bulb yield than 
“Bawku-red” in both locations. For vegetative growth, the highest number of leaves were recorded 
in “Orient” (7.0) and “Trophy” (7.0) at 8 WAT. Highest plant height were also registered in “Red-
creole” (46.4 mm) and “Orient” (60.1 mm) at Sogakope, and Legon respectively. The biggest plant 
stem was obtained both in “Orient” (13.59 mm) and (12.40 mm) at Sogakope and Legon 
respectively. For reproductive parameters, the longest bulb length was obtained in “Trophy” (52.3 
mm) followed by “Red-creole” (49.6 mm). “Trophy” plants yielded bulbs having significantly 
thicker necks (13.09 mm) compared to plants from all the other cultivars. The highest average bulb 
weight was obtained from “Orient” at both sites followed by “Trophy” at Legon. The biggest 
iv 
 
University of Ghana http://ugspace.ug.edu.gh
marketable bulb weight was registered by “Orient” (533 g) followed by “Red-creole” (441 g). For 
bulb quality, “Bawku-red” presented a dark maroon color, “Orient” presented maroon color and 
“Trophy” presented regatta color, while “Dayo” and “Red-creole” both presented the same 
mulberry colour. In terms of bulb form, “Bawku-red”, “Red-creole” and “Orient” produced thick 
flat bulbs, while “Dayo” and “Trophy” produced globe bulbs. At 4 week after harvesting, “Orient” 
(12.85) was significantly higher than the rest of varieties in terms of sugar content followed by 
“Bawku-red” (12.02) at Sogakope. While at Legon, “Bawku-red” (14.93) contained more sugar 
than the other varieties followed by “Orient” (13.20). The varieties “Orient”, “Red-creole” and 
“Bawku-red” had long shelf life compared to “Trophy” and “Dayo” which had short average shelf 
life. For bulb yield, “Orient” gave the highest yield of (8.22 t/ha) at Sogakope and (7.19 t/ha) at 
Legon followed by “Trophy” (8.1 t/ha) at Sogakope and (6.05 t/ha) at Legon. Total bulb yield, had 
positive and highly significant correlation with average bulb weight (1.00**), bulb weight (1.00**) 
and bulb diameter (0.82**) at Sogakope. It also had significant positive association with bulb 
length (0.50*). At Legon, bulb yield had a strong significant positive association with bulb length 
(1.00**), bulb neck (0.94**), bulb weight (0.60**), bulb firmness (1.00**) and plant height 
(0.59** and 0.63**). Variety Orient may therefore be recommended as an additional variety for 
planting in the Southern sector of Ghana. 
 
 
 
 
 
v 
 
University of Ghana http://ugspace.ug.edu.gh
TABLE OF CONTENTS 
DECLARATION ............................................................................................................................. i 
DEDICATION ................................................................................................................................ ii 
ACKNOWLEDGEMENT ............................................................................................................. iii 
ABSTRACT ................................................................................................................................... iv 
TABLE OF CONTENTS ............................................................................................................... vi 
LIST OF TABLES ....................................................................................................................... xiii 
LIST OF FIGURES ...................................................................................................................... xv 
LIST OF ABBREVIATIONS ...................................................................................................... xvi 
CHAPTER ONE ............................................................................................................................. 1 
1.0 INTRODUCTION ................................................................................................................. 1 
CHAPTER TWO ............................................................................................................................ 5 
2.0 LITERATURE REVIEW ......................................................................................................... 5 
2.1 Introduction ........................................................................................................................... 5 
2.2 History of onion .................................................................................................................... 5 
2.3 Onion Varieties ..................................................................................................................... 6 
2.4 Botany of onion ..................................................................................................................... 7 
2.4.1 Vegetative stage .............................................................................................................. 7 
2.4.2 Reproductive and maturity stages ................................................................................... 9 
2.5 Onion Nutrition ................................................................................................................... 10 
2.6 Non culinary uses ................................................................................................................ 10 
2.7 Health risks .......................................................................................................................... 11 
vi 
 
University of Ghana http://ugspace.ug.edu.gh
2.8 Onion Cultivation in Ghana ................................................................................................ 11 
2.9 Climatic requirements ......................................................................................................... 12 
2.9.1 Temperature .................................................................................................................. 12 
2.9.2 Photoperiod ................................................................................................................... 13 
2.9.3 Relative humidity ......................................................................................................... 14 
2.10 Vegetative parameters as influenced by agronomic factors .............................................. 14 
2.10.1 Percentage crop establishment.................................................................................... 14 
2.10.2 Number of leaves per plant ......................................................................................... 15 
2.10.3 Plant height ................................................................................................................. 15 
2.10.4 Stem diameter ............................................................................................................. 17 
2.11 Reproductive parameters ................................................................................................... 17 
2.11.1 Bulb initiation ............................................................................................................. 17 
2.11.2 Bulb growth ................................................................................................................ 18 
2.11.3 Bulb length ................................................................................................................. 18 
2.11.4 Bulb and neck diameter .............................................................................................. 19 
2.11.5 Average healthy and rotten bulb weight ..................................................................... 20 
2.12 Bulb quality parameters .................................................................................................... 20 
2.12.1 Bulb color ................................................................................................................... 20 
2.12.2 Bulb shape .................................................................................................................. 21 
2.12.3 Bulb firmness .............................................................................................................. 21 
2.12.4 Bulb sugar content ...................................................................................................... 22 
2.12.5 Shelf life and storage .................................................................................................. 22 
2.13 Yield parameters ............................................................................................................... 23 
2.13.1 Total and healthy bulb yield ....................................................................................... 23 
2.13.2 Rotten bulb yield ........................................................................................................ 25 
vii 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER THREE ...................................................................................................................... 26 
3.0 MATERIALS AND METHODS ............................................................................................ 26 
3.1 Introduction ......................................................................................................................... 26 
3.2 Description of study areas ................................................................................................... 26 
3.2.1 Climatology and Geology of Sogakope........................................................................ 26 
3.2.2 Climatology and Geology of Legon ............................................................................. 27 
3.2.3 Geographical location of experimental field ................................................................ 28 
3.3 Materials .............................................................................................................................. 28 
3.4 Experimental design and treatments ................................................................................... 28 
3.5 Soil analysis......................................................................................................................... 29 
3.6 Cultural practices................................................................................................................. 30 
3.6.1 Land preparation ........................................................................................................... 30 
3.6.2 Nursery preparation and transplanting ......................................................................... 30 
3.6.3 Onion fertilization......................................................................................................... 31 
3.6.4 Onion irrigation ............................................................................................................ 31 
3.6.5 Onion weeding .............................................................................................................. 31 
3.6.6 Pesticide application ..................................................................................................... 32 
3.6.7 Onion harvesting and curing ......................................................................................... 32 
3.7 Sample preparation .............................................................................................................. 32 
3.8 Physical analysis ................................................................................................................. 33 
3.8.1 Particle Size Distribution .............................................................................................. 33 
3.8.2 Soil Texture .................................................................................................................. 34 
3.8.3 Soil organic carbon ....................................................................................................... 34 
3.9 Chemical analysis ................................................................................................................ 36 
3.9.1 Soil reaction (pH- determination) ................................................................................. 36 
viii 
 
University of Ghana http://ugspace.ug.edu.gh
3.9.2 Electrical Conductivity (EC) ........................................................................................ 36 
3.9.3 Determination of total nitrogen (N) in soil samples ..................................................... 36 
3.9.4 Determination of available phosphorus (P) in soil samples ......................................... 38 
3.9.5 Determination of total potassium (K) in soil samples .................................................. 39 
3.10.1 Vegetative parameters ................................................................................................ 40 
3.10.1.1 Percentage crop establishment ............................................................................. 41 
3.10.1.2 Plant height .......................................................................................................... 41 
3.10.1.3 Number of Leaves per plant ................................................................................. 41 
3.10.1.4 Stem diameter ...................................................................................................... 42 
3.10.2 Reproductive parameters ............................................................................................ 42 
3.10.2.1 Bulb weight .......................................................................................................... 42 
3.10.2.2. Bulb length .......................................................................................................... 42 
3.10.2.3 Bulb diameter ....................................................................................................... 42 
3.10.2.4 Bulb neck diameter .............................................................................................. 43 
3.10.3 Bulb quality parameters .............................................................................................. 43 
3.10.3.1 Bulb colour........................................................................................................... 43 
3.10.3.2 Bulb shape ............................................................................................................ 43 
3.10.3.3 Bulb firmness ....................................................................................................... 43 
3.10.3.4 Bulb sugar content ............................................................................................... 44 
3.10.3.5 Bulb shelf life and storage ................................................................................... 44 
3.10.4 Yield and yield components ....................................................................................... 45 
3.10.4.1 Total bulb yield .................................................................................................... 45 
3.10.4.2 Rotten bulb yield .................................................................................................. 45 
3.10.4.3 Healthy bulb yield ................................................................................................ 46 
3.11 Data analysis ..................................................................................................................... 46 
ix 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER FOUR ......................................................................................................................... 47 
4.0 RESULTS ............................................................................................................................... 47 
4.1 Climatic conditions during the experimental period ........................................................... 47 
4.2 Soil analysis......................................................................................................................... 48 
4.3 Vegetative parameters ......................................................................................................... 49 
4.3.1 Percentage Seedling Establishment .............................................................................. 49 
4.3.2 Number of Leaves per Plant ......................................................................................... 51 
4.3.3 Plant Height .................................................................................................................. 52 
4.3.4 Stem diameter ............................................................................................................... 53 
4.4 Reproductive parameters ..................................................................................................... 54 
4.4.1 Bulb length ................................................................................................................... 55 
4.4.2 Bulb and neck diameter ................................................................................................ 55 
4.4.3 Bulb weight................................................................................................................... 57 
4.4.4 Healthy bulb weight (marketable weight) .................................................................... 57 
4.4.5 Rotten bulb weight (unmarketable weight) .................................................................. 58 
4.5 Bulb quality parameters ...................................................................................................... 59 
4.5.1 Bulb colour ................................................................................................................... 59 
4.5.2 Bulb shape .................................................................................................................... 60 
4.5.3 Bulb firmness ................................................................................................................ 60 
4.5.4 Bulb sugar level ............................................................................................................ 61 
4.5.5 Bulb shelf life ............................................................................................................... 62 
4.6 Yield and yield components ................................................................................................ 63 
4.6.1 Healthy and Rotten bulb yield ...................................................................................... 63 
4.6.2 Total bulb yield ............................................................................................................. 64 
4.7 Correlation analyses ............................................................................................................ 65 
x 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER FIVE .......................................................................................................................... 69 
5.0 DISCUSSION ......................................................................................................................... 69 
5.1 Climatic conditions during the experimental period ........................................................... 69 
5.2 Soil analysis......................................................................................................................... 69 
5.3 Vegetative Growth parameters ............................................................................................ 70 
5.3.1 Percentage Crop Establishment .................................................................................... 70 
5.3.2 Number of Leaves per plant ......................................................................................... 70 
5.3.3 Plant height ................................................................................................................... 72 
5.3.4 Stem diameter ............................................................................................................... 73 
5.4 Reproductive parameters ..................................................................................................... 74 
5.4.1 Bulb length ................................................................................................................... 74 
5.4.2 Bulb neck and diameter ................................................................................................ 74 
5.4.3 Average bulb weight ..................................................................................................... 76 
5.5 Bulb quality parameters ...................................................................................................... 76 
5.5.1 Bulb color ..................................................................................................................... 76 
5.5.2 Bulb shape .................................................................................................................... 77 
5.5.3 Bulb firmness ................................................................................................................ 78 
5.5.4 Bulb sugar content ........................................................................................................ 80 
5.5.5 Bulb shelf life ............................................................................................................... 81 
5.6 Yield and yield components ................................................................................................ 82 
5.6.1 Total, Marketable and Unmarketable bulb yield .......................................................... 82 
5.6.2 Yield comparison between Sogakope yield and Legon ................................................ 84 
5.7 Correlation analyses ............................................................................................................ 85 
CHAPTER SIX ............................................................................................................................. 86 
xi 
 
University of Ghana http://ugspace.ug.edu.gh
6.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................. 86 
6.1 Conclusions ......................................................................................................................... 86 
6.2 Recommendations ............................................................................................................... 86 
REFERENCES ............................................................................................................................. 88 
APPENDICES ............................................................................................................................ 111 
 
 
 
 
  
xii 
 
University of Ghana http://ugspace.ug.edu.gh
LIST OF TABLES 
Table 1: Weather data of the experimental area at Sogakope and Legon ......................... 47 
Table 2: Physico-chemical properties of the experimental sites after harvesting at Sogakope 
and Legon.......................................................................................................................... 49 
Table 3: Seedling establishment percentage of onion grown at Sogakope and Legon ..... 50 
Table 4: Number of leaves per plant of onion crop at Sogakope and Legon .................... 52 
Table 5: Plant height of onion grown at Sogakope and Legon ......................................... 53 
Table 6: Stem diameter of onion grown at Sogakope and Legon ..................................... 54 
Table 7: Bulb length of varieties of onion grown at Sogakope and Legon ...................... 55 
Table 8: Bulb neck and diameter of varieties of onion grown at Sogakope and Legon ... 56 
Table 9: Bulb size and bulb yield of onion varieties grown at Sogakope and Legon ....... 57 
Table 10: Bulb shelf life of onion varieties grown at Sogakope and Legon at 2 weeks after 
storage ............................................................................................................................... 58 
Table 11: Onion bulb condition at 2 weeks after storage for onion cultivars grown at 
Sogakope and Legon ......................................................................................................... 59 
Table 12: Bulb colour of onion varieties grown at Sogakope and Legon ........................ 60 
Table 13: Bulb shape of onion varieties grown at Sogakope and Legon .......................... 60 
Table 14: Bulb firmness of onion varieties grown at Sogakope and Legon ..................... 61 
Table 15: Sugar content of onion bulbs grown at Sogakope and Legon at 2 and 4 weeks 
after harvesting.................................................................................................................. 62 
xiii 
 
University of Ghana http://ugspace.ug.edu.gh
Table 16: Bulb weight of onion varieties grown in Sogakope and Legon at 2 weeks after 
storage ............................................................................................................................... 63 
Table 17: Healthy bulb and rotten bulb yield of varieties of onion grown at Sogakope and 
Legon ................................................................................................................................ 64 
Table 18: Total bulb yield of onion varieties at Sogakope and Legon ............................. 65 
Table 19: Correlation analysis .......................................................................................... 67 
Table 20: Correlation analysis .......................................................................................... 68 
 
  
xiv 
 
University of Ghana http://ugspace.ug.edu.gh
LIST OF FIGURES 
Figure 1: Map showing the location of Sogakope in the Volta Region in Ghana ...... 27 
Figure 2: Plant structure of a young onion plant in the vegetative growth stage 
(Brewster, 1994) ....................................................................................................... 112 
Figure 3: Different onion bulb shapes (1) Flattened (2) Globe (3) High globe (4) 
Spindle (5)            Spanish (6) Flat (7) Thick flat (8) Granex (9) Top (Boyhan & Kelley, 
2008) ......................................................................................................................... 113 
Figure 4: Field trial layout ........................................................................................ 114 
Figure 5: Plot layout indicating number of plants and the harvested area ............... 115 
Figure 6: Soil texture triangle ................................................................................... 116 
 
 
 
 
 
 
  
xv 
 
University of Ghana http://ugspace.ug.edu.gh
LIST OF ABBREVIATIONS 
NS : No Significant 
LSD : Least Significance Difference 
WAT : Weeks After Transplanting 
FAO : Food and Agricultural Organization 
FAOSTAT : Food and Agricultural Organization Statistics 
MoFA : Ministry of Food and Agriculture 
HCDA : Horticultural Crops Development Authority 
UNEP : United Nation Environment Programme 
m : Meter 
mm : Millimeter 
ml : Milliliter 
cc : Cubic centimeter 
cm : Centimeter 
Km : Kilogram 
g : Gram 
t : Tonne 
ha : Hectare 
EC : Electrical Conductivity 
N : Nitrogen 
P : Phosphorus 
K : Potassium 
Max : Maximum 
Min : Minimum 
  
xvi 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER ONE 
1.0 INTRODUCTION 
Onion, (Allium cepa L.), is a herbaceous biennial plant. It belongs to Liliaceae family. Onion is 
indigenous to Central Asia (Kuete, 2017), but is actually grown across the world ( Encyclopaedia 
Britannica, 2018). Biennial plants produce roots, stems, and leaves during the first season of 
production.  During the second season, plant produce flowers, fruits, and seeds, and then complete 
their life cycle. Onion is classified into three categories such as Allium cepa, Allium aggregattum, 
Allium prolilum, which are all diploids (2n = 2x = 16). Onion is ranked the world’s 4th most enjoyed 
vegetables apart from tomato, cabbage and watermelon, the production is 25 million tonnes per 
year (Boukary et al., 2012a). According to National Onion Association (NOA) records of 2011, 
onions are worldwide vegetables among others. Globally, dry onion bulbs around 54 million 
tonnes are grown per year. The crop has being grown in over 134 different countries across the 
world. This represents a doubling in world production over the last ten years (GhanaVeg, 2018). 
In 2011, the National Onion Association estimated the production of onion at about 640 billion 
cedis (105 billion pounds) per year (NOA, 2011). According to the UN Food and Agriculture 
Organisation (FAO) records of 2012, Egypt is the first African producer with 2,208,080 tons and 
the fourth world producer after China (20,507,759 tons), India (13,372,100 tons), and USA 
(3,320,870 tons) (Kuete, 2017). Most African tropical countries import onion bulbs, either from 
Niger, which exports an important part of its 200,000 tons production, or from Europe or South 
Africa (Kuete, 2017). China, India and the USA grow about half of the worlds’ onions production. 
Other countries such as Brazil, Iran, Japan and Russia grow above 1 million tonnes annually.  
 
1 
 
University of Ghana http://ugspace.ug.edu.gh
Onion is an appreciable vegetable crop grown principally for consumption worldwide (FAOSTAT, 
2004; HCDA, 2008; cited by Narla et al., 2011). Furthermore, onion is used not only to maintain 
human life but also to preclude thirst. It can also be used as food when dried and preserved. Several 
books show its utilities as a nourishment and in mummification, medicine, and art (Lawande, 
2012). Onion has also been used to treat skin diseases, ear pain, heart attack and stroke (Ado, 
2001). Onions are the most important horticultural crops rich in vitamin C. It also contains high 
quantity of fiber, with 45 calories per medium onion bulb. It adds abundant flavor to most of daily 
food consumed by human. Generally, onion bulbs contain most of nutritional elements excluding 
sodium, fat, and cholesterol. In addition, onions provide a number of other key nutrients such as 
sugar, protein, minerals and water. Onion contains quercetin (Baghizadeh et al., 2009; Bystrická 
et al., 2013). The quercetin is efficiently used against cancers and cardiovascular diseases (Smith, 
2003; Ro et al., 2015; Gormaz et al., 2015). In addition, it has been reported to be rich in 
phytochemicals especially flavonoids which are medicinal (Javadzadeh et al., 2009; Kuete, 2017).  
 
The most crucial vegetable crop grown in the country is onion. Because it generates high revenue 
to farmers. In Ghana, the cultivation of the crop has been concentrated in the Guinea savannah and 
coastal savannah agro-ecological zones. The Upper East region produces 85% of the total onion 
production in Ghana. Northern Ghana has a competitive advantage in onion production; more than 
20,000 households in northern Ghana grow onion in the dry season for cash. Onion farming in 
northern Ghana is a source of revenue not only for farmers, but also for input dealers, middlemen, 
transporters, and farm labourers (Ghana-Made, 2017). However, the transition zone has been 
found to have very conducive soil and climatic conditions for its production (Dapaah et al., 2014). 
The consumption of onions is increasing in Ghana, the market is growing at an estimated 11% per 
2 
 
University of Ghana http://ugspace.ug.edu.gh
annum, indicating that onion production is sustainable in the future (Ghana-Made, 2017). 
Increasing demand for the crop also brings with it high employment creation opportunities. 
Habitually, Ghanaians use onion bulb in almost every food preparation. In Ghana, consumption 
and production of onion is very high and the country was classified in 2009 as the 123rd in world 
ranking in production with a production of 76,785 Kg/ha (FAO, 2009) and the average bulb yield 
of about 17t/ha (Akrofi et al., 2016). In 2013, MoFA indicated that the country grew onion on a 
surface of 645.23 ha with a total production of 7,542.78 Mt and low average yields compared to 
that of Burkina-Faso and Niger (FAO, 2000; MoFA, 2013). According to NARSP (1994), ‘Bawku 
red’ onion cultivar provides a yield of 7t/ha. But the yield of 30 t/ha, is possible and was recorded 
in the country according to CSIR (cited by Addai et al., 2014). Ghana’s onion consumption needs 
exceed its onion production. Thus about $5 million of dry onion bulb is imported into the country 
per annum (Ghanaweb, 2012). A large quantity of the product is imported into the country from 
Niger and Burkina Faso on a constant basis, even though there is a huge potential to grow good 
quality onions in the country (Assibey-Yeboah, 2018). In fact, successful onion production 
depends on the selection of varieties that are adapted to different conditions imposed by specific 
environment. Low yield is necessary due to the use of poor yielding varieties (FAO, 2000). The 
most popular onion cultivars grown in Ghana include Bawku Red (a local variety) and Early Texas 
Grano and Red Creole, both exotic varieties. Farmers have increased onion production, over the 
last decade, to meet the high demand for the crop in Ghana and the sub-region (Dapaah et al., 
2014). Hence, there is a need for the introduction of new varieties to enhance productivity. 
Therefore, the present research was conducted to evaluate the yield performance of four newly 
introduced onion cultivars namely, Dayo, Trophy, Red-Creole, and Orient against the commonly 
grown variety ‘Bawku-Red’ under two different ecozones.  
3 
 
University of Ghana http://ugspace.ug.edu.gh
The specific objectives of the study were to: 
i.)  identify a variety or varieties that yield higher than the local variety under field 
conditions, and 
ii.) identify the most suitable ecozone for production of higher yield of onion. 
 
 
 
 
 
 
 
 
 
 
 
4 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER TWO 
2.0 LITERATURE REVIEW 
2.1 Introduction  
The most essential factors that affect onion production are photoperiod and temperature. These 
environmental factors clearly influence not only onion growth but also its development. The 
correlation between the physiological characteristic, the genetical potential of the seed, conditions 
in the environment and management determines the performance of onions (Jilani and Ghaffoor, 
2003; SAKATA, 2014). The determination of a cultivar selection for a specific area is principally 
due to the interaction of these environmental factors. On the contrary, fertilization, irrigation, crop 
protection, weeding and harvesting etc., affect quality growth and yield of onion bulbs (Brewster, 
2008; USAID, 2009). 
 
This section will be based on botany, origin, importance, climatic conditions, plant morphology 
and phases of onion growth. Growth and yield performance, quality and shelf life of onions will 
also be discussed. 
 
2.2 History of onion 
Onion is believed to have originated from central Asia (Iran and Pakistan).  Wild onions existed 
long before farming was invented. Onions have been among the earliest cultivated crops. As early 
as 5,000 years ago, Chinese grew onions in their gardens.  The oldest Vedic writings from India 
referred to this practice. In the sixth century B.C., the Charaka Sanhita celebrated the onion as 
medicine, a diuretic (water pill), good for digestion, the heart, the joints as well as the eyes (All 
About Onion, 2018).  
5 
 
University of Ghana http://ugspace.ug.edu.gh
Onions (Allium cepa L.) and shallots (Allium ascalonicum) have been put to almost identical use 
in Ghana and one can hardly talk about onions without mentioning shallots as well. Though the 
origin of shallots has been traced by Sinnadurai (1973) that of onions is not quite well known. The 
onion commonly found in the markets of Ghana comes from the Upper East or the Upper West. 
The variety is called 'Bawku red' (Sinnadurai and Abu, 1977). According to Adomako (1959) 
onion which was introduced into Ghana around 1930 was first grown at Bugri, near Bawku in the 
Kusasi District of the Upper West Region, and from there it spread to other parts of the Northern 
and Upper East regions. It is now popular in the big urban towns in Ghana where the crop is grown 
more as green onion than for bulbs. The Kusasi District and the areas surrounding it still remain 
the most important for the cultivation of the variety.  
 
2.3 Onion Varieties 
Diverse varieties of onion exist in agriculture such as yellow, red, white and bunch onions. They 
are categorized according to bulb size, form, sugar content and firmness (All About Onion, 2018).  
 
Yellow Onions: about 87% yellow onions is dedicated to production in America. Yellow Onions 
are highly rich in flavor and are reliably reserved for cookery. When cooked, the bulb color of 
yellow onions immediately changes to dark brown. These onion varieties are the sweetest onion 
(All About Onion, 2018).  
 
Red Onions: they have excellent color and good for fresh uses. In America, approximately 8% of 
the crop is dedicated to red onions production. They can also be eaten raw in some of foods such 
as sandwiches, ‘gari’ and salads (All About Onion, 2018). 
6 
 
University of Ghana http://ugspace.ug.edu.gh
White Onions: they are more often used in preparation of salads, sauces (white sauces). White 
onions present gold colour and sweet flavor after preparation. About 5% white onions is commonly 
used in United States of America.  
 
Bunch onions: they are also known as Japanese bunching onion with Allium fistulosum the 
scientific name or nomination. A. fistulosum can be assimilated to green onions which is grown 
only for it leaves. They are often used exclusively as scallions (All About Onion, 2018).  
 
Bettson (1961) observed that unlike the 'Bawku red' variety they also deteriorate easily and farmers 
had to sell them immediately after harvest. Since spoilage is less in the 'Bawku red' variety, they 
fetch better prices. According to Sinnadurai and Abu (1977), foreign cultivars like Texas Grano, 
Texas Early Grano, Eclipse, Bermuda, Crystal White Wax, Red Creole, Tropical and Bombay Red 
have been tried and found not to be very suitable. Texas Early Grano, Tropical and Bombay Red 
have shown some promise in certain years but this depends very much on the climate. The 'Bawku 
red' variety needs to be studied in detail and if done, a good cultivar can be obtained for the country. 
According to Ahmed et al. (2013), the difference among cultivars is related to genetic factors make 
up by the used cultivars (Akhtar, Ehsan (2002); Gemma et al. (2007); Kandil et al., (2010) and 
Soleymani and Shahrajabian (2012) 
 
2.4 Botany of onion  
2.4.1 Vegetative stage 
Allium cepa, is onion specie largely produced among others of the genus Allium. Apart from Allium 
cepa, several other species such as Allium fistulosum, Allium proliferum and Allium canadense 
7 
 
University of Ghana http://ugspace.ug.edu.gh
belong also to the genus so-called Allium. All these various species of onions are produced for 
diverse purposes such as nutritionals. Onion is classified among perennial crops. Usually, onion is 
considered as an annual vegetable plant. Therefore, onions are harvested when bulbs are fully 
formed and matured. The swelling of onion bulbs depend on the day length. Before the bulb start 
to swell, the required day length must be reached (PROKON, 2016). Onion plant stem usually 
carries one or more white blossom(s). The concentric leaf physiologically and morphologically 
change by swelling to produce the underground edible bulb (Encyclopaedia Britannica, 2018). 
From the rhizosphere of the plant roots extends for a short way underground. The leaf base, 
progressively accumulate food reserves as the bulb matures, resulting in bulb swelling. Onion 
flower has spherical umbel shape with black and triangular seeds (PROKON, 2016). The 
classifications of onion varieties are based on day length required for bulb formation, market use 
(green, fresh bulbs and dehydrated bulbs) bulb colour (such as Red, white, yellow and purple skin) 
and elongated or globe shaped (Kyofa-Boamah et al., 2000; Necola, 2007). They undertake three 
development phases (leaf and bulb formation and maturity) throughout the growing season 
(Kyofa-Boamah et al., 2000; FAO, 2005; cited by Alidu, 2013).  
 
Prior to bulb formation, Jones & Mann (1963) and Brewster (2008) described onion crop in the 
vegetative phase. First of all, the stem which occur below the soil surface, is a planate disc. It also 
contains the shoot apex inside plant stalk where all new leaves and roots are developed. The 
components of each leaf are blade and sheath. The leaf sheath appears first as the stem of the plant 
or a pseudo stem. The development of the leaf sheath which is covered by the growing point, leads 
to the formation of a tube enclosing the youngest developing leaves. Leaves are newly developed 
and emerge close to the apex.  At the base of the stem appear new roots, but only the primary root 
8 
 
University of Ghana http://ugspace.ug.edu.gh
emerges from the seed. Onions attempt to produce lateral branches from the buds in the leaf axils. 
These branches can result in increasing onion bulbs yield. As soon as the day length is long enough 
as well as the temperature is extremely high, bulb initiation will occur and the young developing 
leaves cease to form bladed leaves but only bladeless leaves will form. Onion bulb is formed from 
these swollen bladeless sheaths (Bosekeng, 2012) (Appendix 2). 
 
2.4.2 Reproductive and maturity stages 
The life cycle of onion crop can be categorized into three phases (Brewster, 1990 and Bosekeng, 
2012). These developmental stages are the seedling establishment, vegetative leaf growth and bulb 
stages (Grauert, 2014). Onion seed begins to germinate few days after sowing (Brewster, 1994). 
Primary root begins to grow under the soil as germination starts and the cotyledon emerges on the 
surface of the soil. The leaf forms and develops when the cotyledon is fresh and young. This is 
called ‘first leaf stage’. The second and third true leaf appear when the cotyledon begins to fade 
and drops. This happens after the cotyledon dies. The appearance of leaf four leads to the thickness 
of the stem diameter and the first leaf begins to shrivel. This is also known as ‘onion plant leek 
stage’. This allows the second leaf to start senescing from the tip and the fifth, sixth and seventh 
leaves to appear. According to Brewster (1994), plant reaches its maximum height during the so-
called bulbing stage. Onion bulbing stage announces the initiation of bulb while leaf two and three 
senesce and leaf eight to thirteen appear.  
During bulb swelling stage, leaves four, five and six senesce progressively. This pushes leaves to 
fold and the formation of the dry outer skin of bulb. The neck becomes hollow as onion crop fall-
down and tissues are no more turgid and soft. Therefore, the leafage collapse and the size of bulb 
9 
 
University of Ghana http://ugspace.ug.edu.gh
ceases to grow. During bulb ripening stage, the color of outer skin of the bulb changes and the skin 
becomes dry, cure and set while leaves die and dehydration takes place (Brewster, 1994). 
 
2.5 Onion Nutrition 
Onions are chief food plants in which the food is stored in a bulb (Craig, 2010). Onion is grown 
not only because of it bulbs but all so because of it green leaves. Green leaves can be harvested 
and commercialized. They are usually used in salads, while bulbs are eaten raw or cooked (Craig, 
2010). Onions are super-healthy vegetable. Onion bulbs is a source of fiber, folic acid and vitamin 
C and B helping the production of strong and new cells (Jarzabkowski, 2017). A medium size of 
onion bulb contains about 45 calories. In addition, onions provide flavor to various food. Onions 
bulbs contain no sodium, fat, and cholesterol (Jarzabkowski, 2017; FDA, 2018). According to 
Anonymous (2005), they contain low sodium. They are rich in sulphuric compounds, flavonoids 
and phytochemicals (Anonymous, 2005; Craig, 2010; Jessie, 2017). Onions are highly rich in 
antioxidants. This makes onion bulbs sweet and aromatic (Jessie, 2017) (Appendix 1). 
 
2.6 Non culinary uses 
Large cell characteristics of onions make it easy to view under low magnification. Its single layer 
cell nature makes the epidermis of the bulb easy to separate for breeding, educational and 
experimental purposes (Suslov et al., 2009; Xu et al., 2014). In biology education, onions bulbs 
are used to describe cell structure using a microscope (Anne et al., 2007). Onion juice has been 
known to be used as a moth repellent because of its pungent smell and can also be used to prevent 
insect bites by rubbing on the skin.  Onion can promote hair growth when applied to the scalp and 
reduce freckling when applied to the face. Some people polish their glass and copperware using 
10 
 
University of Ghana http://ugspace.ug.edu.gh
onion and others apply it to iron to prevent rust. The resulting liquid obtained when  boiling water 
is poured on sliced onions and then left to cools can prevent pest (i.e. moles and insects) infestation 
when sprayed on plants (Fem et al., 2013). Yellow brown dye is also gotten from onion skins 
(USPO, 2011).  
 
2.7 Health risks  
Eating onion can cause problems for some individual, but not seriously. National Digestive 
Diseases Information Clearing house reports that consuming onions can cause bloating of an 
individual, as well as accumulation of gases in the stomach of the individual because of the 
carbohydrate content it contains. The consumption of raw onions has been known to cause 
heartburn in people who chronically suffer from gastric reflux disease or heartburn (America 
Journal of Gastroentrology, 1990). High consumption of green onions is likely to interfere with 
drugs that cause blood thinning. The high content of K in onions inhibits the function of a blood 
thinner. According to Jarzabkowski (2017), when onions are sliced or chopped, it gets spoilt faster 
than the whole bulb. A study conducted in 2015 showed that yellow onions not refrigerated 
facilitated the growth of E.coli and salmonella and those that were refrigerated showed no such 
growth (Jessie, 2017). 
 
2.8 Onion Cultivation in Ghana 
Onion production areas in coastal savannah and transition zones of Ghana include Sogakope and 
Akatsi in the Volta region, Ashaiman and Dawhenya in the Greater Accra, Nsawam which is in 
the Eastern Region of Ghana and Prestea in the Western part of Ghana (Awuah et al., 2009). In 
the Upper East Region of Ghana, farming families active in onion production are at Bawku West 
11 
 
University of Ghana http://ugspace.ug.edu.gh
and Garu Tempane Districts (Trias, 2010). Onion yields in the Upper, Northern and Southern 
Regions of Ghana are 15-25t/ha and 5-15t/ha respectively (Norman, 1992; cited by Alidu, 2013). 
The short day, local red cultivars (i.e. ‘Red Creole’, ‘Bawku Red’ and ‘Malavi’) are the commonly 
grown cultivars in Ghana. Other exotic cultivars such as Texas early Grano, Crystal White Wax, 
Lisbon White, Yellow Flat, Suttons, Australian Brown, Early Cape and Market Winner were in 
the past introduced into the country (Kyofa-Boamah et al., 2000; Awuah et al., 2009). Cultivars 
that performed best (Texas Early Grano, Red Creole, Market Winner and Australian Brown) have 
been maintained to date (Awuah et al., 2009). 
 
2.9 Climatic requirements 
2.9.1 Temperature 
Onions are a cool season crop. Onion seeds germinate at an optimum temperature range between 
10 to 35oC, the maximum temperature requirement is 40oC. It is also most adapted to a growing 
season where air temperature ranges from 13 to 24oC. Bulb formation requires high temperatures, 
whiles the early stages of onion plant growth require low temperatures. Seedlings are tolerant to 
lower temperature down to -1oC and cool weather conditions during its early growth stages, though 
the onion plant is very tolerant to frost.  Lower temperatures facilitate the seed stalks (bolting). 
However, onion bulbs grow faster at warmer temperatures than cooler temperatures. The onion 
bulbs grow quicker at warm than at cool temperatures. When temperatures increase to 40oC 
bulbing is slowed. Development and performance of the onion plant is controlled by the climatic 
condition such as temperature at all stages (Abu-Rayyan and Abu-Irmaileh, 2004; Coolong and 
Randle, 2003 and Ansari, 2007).  
 
12 
 
University of Ghana http://ugspace.ug.edu.gh
2.9.2 Photoperiod 
Onion varieties will initiate bulb formation based on day length; this is because they are sensitive 
to photoperiod (USAID-Inma, 2012). Bulb initiation occurs when onions react to day length. The 
leaves of onion plant are receptive to photoperiodic stimulus (Okporie & Ekpe, 2008). The type of 
onion variety dictates the day length required for bulb formation. This day length ranges from 12 
to 16 hours (Norman, 1992; Dawling et al. 2006; Obeng-Ofori et al., 2007). According to 
GhanaVeg (2018), 12 to 15 hours day length are needed for the formation of onion bulb, they also 
require high temperatures. The outer leafage tends to dry and form a preventive skin, during bulb 
maturity (Brewster, 1994). Onion varieties adaptation to a particular area of production is based 
on day length of the site and the specific cultivar to be used (USAID-Inma, 2012).  
 
The time of year the onion is planted is dependent on the climate; consequently, onions are 
cultivated at different times of the year. The climate also has an effect on the type of onion grown. 
Short day and long day are the two main varieties of onion. Short day varieties are mostly 
cultivated in warmer regions and do perform well at 12 hours of daylight. Whereas, the long day 
types are in colder climates and perform well at day length between 15-16 hours (All About Onion, 
2018).  
In Ghana, only short day cultivars and intermediate day onion varieties can be grown, this is due 
to the fact that 12 hours 25mins is the longest average day length (Sinnadurai and Abu, 1977). If 
a variety is exposed to insufficient photoperiod, bulbing is affected. In this case, non-bulbing plants 
will have thick necks, when onion cultivars are not given the required day length optimum for 
plant growth (Wiles, 1994; González, 1997; SAKATA, 2014). Premature bulbing will occur in 
young plants when a cultivar is exposed to longer day length than it requires, even if it is for a few 
13 
 
University of Ghana http://ugspace.ug.edu.gh
days. This will result in the production of smaller bulb sizes and lower yields (Wickramasinghe et 
al., 2000; SAKATA, 2014).  
 
 2.9.3 Relative humidity 
Plant roots absorption of water and photosynthesis rate decreased under high atmospheric water 
vapor due to the stomata closure partially or completely (Brewster, 2008). Onion bulb formation 
requires drought conditions. Leaves diseases occurrence, for instance leaf blight (Botrytis 
squamosa) decreases under dry conditions (Msuya et al., 2005).  At harvesting and during drought 
conditions onion plant leaves rapidly dry up. Consequently bulbs formed are firm as they have lost 
all moisture when the neck of the bulb dried off (Bosekeng, 2012). Bulb storability is highly 
influenced by the prevailing high relative humidity (RH) (Brice et al., 1997). When relative 
humidity is high, post-harvest bulbs will sprout and rot (Brewster, 1994) which further reduce the 
marketable yield of onions. 
 
2.10 Vegetative parameters as influenced by agronomic factors 
2.10.1 Percentage crop establishment 
Rizk (1997) reported that high percentage crop establishment contributed generally to enhance 
crop growth and hence high leaf number per plant. According to Tweneboah (2000), good land 
preparation coupled with judicious application of inorganic and organic fertilizers and quality seed 
usage will result in a higher percentage crop establishment. 
 
14 
 
University of Ghana http://ugspace.ug.edu.gh
2.10.2 Number of leaves per plant 
Research conducted by Ibrahim (2010), indicated that the application of fertilizer to soil can 
increase leaf number from 6 to 11 with an average of one leaf per week. The boost in leaf number 
per plant was achieved because both organic and inorganic fertilizers supply the soil with high 
nutrients especially nitrogen which significantly support vegetative growth (Blay et al., 2002). The 
number of leaves also depend on the amount of the nitrogen applied and possibly the source of the 
nitrogen (Akuamoah-Boateng, 2016).  
 
A minimum temperature of 6°C is necessary for leaf canopy development and leaf growth will 
cease if temperatures fall below 6°C. When temperature increases from 6 to 20°C relative rate of 
growth of the leaf will increase linearly. A further boost in temperature of the onion will cause rate 
of growth to start dwindling and then will stop when temperatures go above 26°C (Bosekeng, 
2012). Addai and Anning (2015) and Tsitsia (2012) observed that the number of sprouts had an 
influence on the increase in leaf number. Furthermore, Addai and Anning (2015), indicated that 
when the leaf number and bulb number was high, the sprout number will also be high. Iannotti 
(2008) also indicated that when the number of leaves of an onion plant was high the bulb number 
at harvest will consequently be high. The same observation was also made by Perez et al. (1996). 
 
2.10.3 Plant height 
Abdissa et al. (2011) reported that adding 69 kg/ha of nitrogen fertilizer increased onion plant 
height by 10% compared to the control. Also, the nutrients content in soil could be a cause for 
difference in plant height, especially nitrogen and sulphur (Nasreen et al., 2007) which have been 
15 
 
University of Ghana http://ugspace.ug.edu.gh
proved for their enhancement effect on the vegetative growth of onion. Abdissa et al. (2011) also 
indicated that the addition of NPK 15-15-15, significantly increased growth of onion plant. 
 
Bhatt et al. (2007), observed that when plants were grown at 45 and 60 days higher plant height 
was obtained, regardless of sowing them late. This was confirmed by Ahmed et al. (2013), who 
stated that the transplanting dates of seedlings of onion caused particularly significant effects on 
plant height. He confirmed again that the highest values on plant height resulted from transplanting 
seedlings early. According to Bosekeng (2012), larger plants are obtained when growth period is 
lengthened and this can occur when early sowing is done. Ahmed et al. (2013) reported that the 
genetic make-up of onion varieties accounted for the differences between cultivars. Abdelkader 
Abou Azoom et al. (2014), reported variations in plant height ranging between 42.61 – 76.95 cm 
depending on cultivar. Similar variability in plant height between onion varieties was observed by 
Ibrahim (2010) and Trivedi and Dhumal (2010). 
According to Mohanty and Prusti (2001), the difference in height of onion plant though mainly 
attributed to the genetic potential is also influenced by environmental factors especially 
temperature and photoperiod (Tesfay et al., 2011).  
 
Tsitsia (2012), reported also that the size of bulb affected plant height with larger bulbs recording 
higher plant height and length of leaf as compared to others. Fuseini (2012) also reported that 
vegetative growth was high in medium bulb comparative to large and small bulbs. Addai and 
Anning (2015), revealed that vegetative growth and yield were heightened in large bulb size and 
was reduced in smaller bulbs size. The leaf number can determine the critical size of the plant. 
16 
 
University of Ghana http://ugspace.ug.edu.gh
Khokhar et al. (2007) observed that the size of an onion plant is sensitive when it develops 7 to 10 
leaves.  
 
2.10.4 Stem diameter 
According to Cramer (2003), date of sowing has an influence on the size of onion plants formed. 
Hasegawa et al. (2005) obtained an increase of diameter of Arisaema ternatipartitum after addition 
of chitosan in cultural substrate. 
 
2.11 Reproductive parameters 
2.11.1 Bulb initiation 
Onion bulb formation requires several factor combinations such as cultivar, plant size, 
temperature, light quality and fertilizer (Sinclair, 1989 and Mondal et al., 1986c).  Onion bulb 
initiation commences as soon as the day length period is more than the minimum required by a 
specific cultivar (Quadir & Boulton, 2005). Several cultivars during bulb initiation require long 
days. When this is not met, onion will not form bulbs. According to Bok et al. (2003) ‘Australian 
Brown’ intermediate day length cultivar performed well in South Africa. But the same cultivar 
grown in Botswana could not do well. As soon as onions crop meet the day length required, bulbs 
formation is initiated. The ratio of the red to far-red light influences the bulbing rate in a particular 
photoperiod rate. The red:far-red ratio decreases with an increased LAI accelerating bulb initiation 
(Mondal et al., 1986c). Bulb formation is also influenced by temperature. When temperatures are 
high, between 25 and 27°C bulbing is enhanced, earlier bulb initiation and maturation is facilitated. 
At short photoperiod during drought season onions will start with bulb formation (Lancaster et al., 
1996). This depends on the interaction between day length and temperature. When plants are large 
17 
 
University of Ghana http://ugspace.ug.edu.gh
coupled with warm temperatures onion plants will start forming bulbs earlier. Ansari (2007) 
showed that the best time for onion to produce bulbs was late February. Ahmed et al. (2013) made 
similar recommendations.   
 
2.11.2 Bulb growth 
Applying too much NPK will hinder onion bulb performance (growth and development) (Rahn et 
al., 1996). Bulb growth is affected by number of leaves which are produced before bulbing. Onion 
leaves are the fundamental sources of assimilates for the enlargement of bulbs (Mettananda & 
Fordham, 1999; Valenzuela et al., 1999). The leaf area is very crucial for photosynthesis and bulb 
growth. The time taken for leaves to develop and mature influences the leaf area and hence 
efficient photosynthetic capacity and potential for bulb growth (Lancaster et al., 1996). 
Photosynthesis is the production of sucrose which will be transported and stored in the structural 
and storage tissue of the plant. This sucrose is converted to glucose and fructose by the specific 
enzyme namely ‘invertase’ during the development of onion bulbs (Brewster, 2008). Therefore, if 
an onion cultivar is sown on a date which allows for long duration of vegetative growth, the better 
the growth of bulbs will be and ultimately better yield will be attained (Bosekeng, 2012). 
 
2.11.3 Bulb length 
Yadav et al. (2003) and Reddy (2005) reported that N fertilization increased bulb length of onion. 
Yohannes et al. (2013) also showed that N when applied at different rates had a significant effect 
on the mean bulb height. He added that among the different levels of N evaluated, the maximum 
rate of N at 150 kg/ha gave the highest mean length of bulb which was 12% more than the control. 
In an experiment conducted by Sultana et al. (2014), a combined addition of N from organic and 
18 
 
University of Ghana http://ugspace.ug.edu.gh
inorganic sources to the soil resulted in increased length of the bulb. The highest length of   bulb 
length at 2.8 cm was obtained when 80 kg N/ha obtained from urea and 40 kg N/ha substituted by 
cow dung was applied to the soil. But, Abdissa et al. (2011), on contrary, observed no significant 
effect on bulb length when N fertilizer was used.  
 
2.11.4 Bulb and neck diameter 
The bulb sizes of onion vary from a medium of 40-69 mm to an extra small size of 10-34 mm , a 
small size of 35-39 m, a large size of 70-89 mm and extra-large of >90 mm. Consumers like 
medium size onions that will attain higher prices on the market than the extra small (Bosch Serra 
& Currah, 2002). Bulb neck diameter is also an important element among others to consider in 
bulb quality and storage. Gautam et al. (2006) reported that bulbs with thinner necks tend to store 
longer than bulbs with thicker necks. The reason is that, bulb with big necks require enough time 
to dry. In addition, they are more and easily infected by Pseudomonas gladioli pv. alliicola 
burkholder which cause bacterial soft rot in storage (Peters et al., 1994; Wright & Grant, 1997). 
Onion growers prefer to produce and sell onion in a specific market. They grow medium size bulbs 
for fresh market and good revenue (Bosch Serra & Currah, 2002) and thinner necks for good 
storage (Mohanty & Prusti, 2001). There is also market for thick bulb sizes with low price. Onion 
bulb is the widely consumed part of the plant that is why its characteristics interested several works 
which insisted on the existence of genetic difference between the varieties of onion in diameter of 
neck (Gautam et al., 2006). According to Anil (2008), five major loci (i.e. I, C, G, L and R) control 
the colour of onion bulb. Also, similar finding was obtained on onion between 18 genotypes in 
Spain (Rivera-Martinez et al., 2005), 10 genotypes in Bangladesh (Nilufar, 2009) and 21 ecotypes 
in Nigeria (Boukary et al., 2012b). Abdissa et al. (2011), reported that irrespective of the rate of 
19 
 
University of Ghana http://ugspace.ug.edu.gh
application, nitrogen fertilization increased bulb diameter of onion by about 12% compared to the 
control. It was further reported by Mohammadi-Fatideh and Hassanpour-Asil (2012) that bigger 
bulb sizes were produced when nitrogen was applied at the rate of 150 kg/ha. There was however 
no significant difference between the bulb diameter from 100 kg/ha and 150 kg/ha treatments.  
 
2.11.5 Average healthy and rotten bulb weight  
According to Abdelkader Abou Azoom et al. (2014), data of bulb weight indicated that ‘BHP’ cv. 
produced the biggest bulb of 155.02 g followed by MA (139.25 g) and KR (110.43 g), whereas 
‘Z6’ cv. had the minimum weight of bulb (63.13 g). Similar result was observed in others varieties 
of onion (Mohanty and Prusti, 2001; Mohanthesh et al., 2008; Trivedi and Dhumal, 2010; Dwivedi 
et al., 2012) and garlic (Volk, 2009). Similarly, Bosekeng (2012), also confirmed that when onion 
plants are sown early, they tend to have a longer growth period which then results in the formation 
of larger bulbs.  
 
2.12 Bulb quality parameters 
2.12.1 Bulb color  
Bettson (1961) reported that most foreign cultivars which were light in colour, were not acceptable 
to the local population. According to Grauert (2014), nitrogen reduction results in improved bulb 
quality (skins, firmness etc.). The Advisory Committee on vegetable crops of Atlantic Canada 
(2017), noted that when onions are cured at temperature ranges between 24 to 32oC and an 80% 
relative humidity it develops the best skin color. 
 
20 
 
University of Ghana http://ugspace.ug.edu.gh
2.12.2 Bulb shape 
Onion bulbs shape is based on the type of cultivar and is a very relevant marketing characteristic. 
Consumers’ prefer circular bulb both in South Africa and for export market (Bosch Serra & Currah, 
2002; Eksteen et al., 1997 ;). Bosekeng (2012), reported that the type of variety influenced onion 
form. According to Jilani & Ghaffoor (2003) and Hasegawa et al. (2001) all onion variety has a 
specific bulb shape. Onion bulb present different form such as flat, globe and sphere. Plant 
population and date of sowing affect onion bulb shape (Grant & Carter, 1994). According to them, 
the bulb shape index changed from 1.02 to 1.06, when the population of plants increased 
dramatically. Shape of bulb can be identified visually (Figure 2: Appendix 3) or by using the bulb 
shape index (Bosekeng, 2012).  
 
2.12.3 Bulb firmness 
Bulb firmness in addition contributes to consumers’ preference of bulb quality. It also influences 
the storability of onions (Mallor et al., 2011). Bulb firmness is largely affected by the composition 
of the cell walls such as physical and chemical composition. Dry matter content and total soluble 
solids (TSS), play an important role in bulb firmness during harvest (Coolong et al., 2008). They 
reported that the differences in dry matter content could lead to an increase in cell water content 
and cell turgor which results in firmer plant tissue. Bulb firmness varies during storage. This is 
affected by the activities of pectinases. Pectinase is an enzyme which control the composition of 
pectic polysaccharides and bind to free calcium ions, increasing bulb firmness.  
 
Lancaster et al. (2001a) and El-Tantawy & El-Beik (2009) respectively reported that sulphur or 
copper  affected onion bulbs firmness. This was supported by Nasreen et al. (2003) who indicated 
21 
 
University of Ghana http://ugspace.ug.edu.gh
that sulphur or copper fertilizers play a role of onion dry matter accumulation, strengthen bulb 
cells and increase onion bulb shelf life so that they can be stored long. In addition, low application 
of sulphur initiates softer bulbs (Lancaster et al., 2001b). Similar finding was reported by Grauert 
(2014), that nitrogen reduction does not lead to less yield but improved quality (skins, firmness 
etc.). Agronomic practices such as irrigation has influence on onion bulb firmness (Larsen et al., 
2009). They added that small bulbs are extremely firm compared to big size onion. Bettson (1961) 
reported that most foreign cultivars are not very firm when mature. According to STARKE 
AYRES (2014), the curing process allows for development of scale leaf colour and firming of the 
bulbs. When the rates of nitrogen is high, bulb firmness reduces, because of the softness of internal 
tissue (GhanaVeg, 2018). 
 
2.12.4 Bulb sugar content 
Onion bulb sugar content is largely affected by storage temperature. Storage temperature has a 
direct relationship with sugar content. It is very essential to note that variation of bulbs sugar 
content is affected by storage temperature (Benkeblia et al., 2002). The same observation was 
made by Hurst et al. (1985).  
 
2.12.5 Shelf life and storage 
It is clear that dry matter content and dormancy are some of the genetic factors which affect bulb 
shelf life (Hygrotech, 2009a & b). Thus photoperiod in bulb storage indicate whether bulb can be 
stored longer or shorter. He reported again that intermediate day cultivars (6-7 months) store better 
than short day cultivars (4 months). According to Galvan et al. (1997), onion bulbs sown earlier 
have enough time to grow well, to produce large leaves. Large leaf areas effectuate better 
22 
 
University of Ghana http://ugspace.ug.edu.gh
photosynthesis and accumulate enough assimilates for the plant to complete well it life cycle and 
the bulbs to store well. Bosekeng (2012) indicated that harvesting onions bulbs too early cause 
lack of growth inhibitors translocation to onion bulbs.  
 
Curing consists of drying harvested onion bulbs roots, outer skins and neck. The outer skins protect 
onion bulbs against postharvest pathogens during handling and storage. This postharvest practice 
increases bulbs shelf life and reduces all types of bulbs infection (Wright & Grant, 1997). The 
percentage of weight loss is minimized with long shelf life cultivars and maximized with short 
shelf life cultivars. Ramin (1999), observed that the loss of bulbs water content can be reduced 
with 65 to 75% relative humidity when stored. 
Onions bulbs shelf life and storage ability of a particular cultivar are very essential for onion 
growers so that they can stock onions until there is a shortage or lack of onion on the market 
(Joubert, 1997). Bulbs shelf life and storage depend also on it firmness. Because firmer bulbs store 
better (up to one month longer) than softer bulbs (NAD, 2009).  
 
2.13 Yield parameters 
2.13.1 Total and healthy bulb yield 
Several factors such as light interception, sowing date, plant population, and cultivar and soil 
fertility influence onion yield. The aim of any producer is to obtain ultimately high yields. This so 
called high yield depends largely on plant vegetative growth. Therefore, better vegetative growth 
results in better performance of onion in terms of yield (Ibrahim, 2010). Sowing date contributes 
enough to bulbs yield. When this is delayed, plant mature early, resulting in small bulbs and lower 
yields. Soleymani and Shahrajabian (2012) stated that total yield, was significantly influenced by 
23 
 
University of Ghana http://ugspace.ug.edu.gh
cultivars. Abdelkader Abou Azoom et al. (2014) showed that the yield of onion varieties ranged 
from 15.42 to 36.88 t/ha and that some foreign varieties had slightly higher yield than that of the 
commercial variety ‘BHP’. Bettson (1961) conducted experiments to compare the 'Bawku red' 
variety with foreign cultivars and reported that foreign cultivars performed significantly better than 
the 'Bawku red' in the Bawku District and recommended some foreign cultivars to farmers. The 
recorded variations of varieties in marketable yield could be as a result of the variations in genetic 
make-up (Pavlovic et al., 2003) and/or agro ecological adaptations.  
 
According to Sinnadurai and Abu (1977), the yield is very much dependent on the climate during 
the growing season and thus is very unpredictable. Very often the yield does not exceed 2,241.8 
kg but when the weather is cool during the night and warm during the day, higher yields can be 
obtained with fertilizers. The low yield may also be an inherent character since no selections have 
been made for bulb size and colour. Ali et al. (2007) reported that unavailability of good quality 
seeds and inability to develop improved varieties have attributed to the lower yields obtained. 
Shaikh et al. (2002), confirmed that crop yield can be improved up to 30% if seed varieties are 
improved. Also, onion yields are affected by soil moisture content, the use of low yielding 
varieties, harsh climate and poor soils are the causes of low productivity of vegetables, including 
onions in Botswana (Baliyan and Kgathi, 2009). Jilani and Ghafoor (2003) and Kimani et al. 
(1993) reported that the genetic make-up, as well as the environment results in various cultivars of 
the same species grown in the same environment giving different yields. Apart from the 
development of new varieties and good management and cultural practices, an evaluation of the 
available onion varieties is key to the sustainable strategies which will help improve the production 
and productivity (Wiles, 2006; Baliyan, 2014). 
24 
 
University of Ghana http://ugspace.ug.edu.gh
2.13.2 Rotten bulb yield 
Lacy and Roberts (1982) suggested that Fusarium basal-rot not only reduces the yield of plants, 
but also reduces the size of bulbs produced by affected plants. According to Adongo (2015), there 
was a major increase in all the postharvest diseases in the wet season. Raju and Naik (2007), 
indicated that the above observation was due to optimum temperatures and high relative humidity 
that occurs during the wet season. Awuah et al. (2009) and Alidu (2013) reported that Malavi was 
least susceptible while Red Creole was moderately susceptible, Texas Grano and Bawku Red were 
highly susceptible to the onion bulb rot diseases. When watering it is important to keep the soil 
moist, not wet. Rot of onions occurs easily in soggy soil (All about Onion, 2018). After the onions 
have been cured, shears can be used to remove the tops ensuring that about an inch of the bulb is 
left above. Dry and soft brush should be used to remove the dirt off the onion without using water 
or damaging the outer dry skins. Onion can then be stored for 3-4 months in a cool, dry place, 
preferable a basement or root cellar. Ideally, onion can be kept at temperature ranges between 
1.67oC and 4.44oC. As long as the temperature in the storage facility stays below 12.78oC, onion 
bulbs are unlikely to rot (All about Onion, 2018). 
 
 
 
 
 
 
 
25 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER THREE 
3.0 MATERIALS AND METHODS 
3.1 Introduction 
This section is focused on the materials and methods used in this work as well as the description 
of the study areas. The methodology describes the data sources, data collection techniques and 
data analysis as well as the measures and the statistical analysis and tools employed. The 
description of the study area on the other hand includes the location in space, climate and geology.  
 
3.2 Description of study areas 
3.2.1 Climatology and Geology of Sogakope  
Sogakope climate identifies between the dry Equatorial climatic regions of Ghana. Sogakope is 
considered as one of the drought regions in the country. Southern part of the main Volta Basin, 
including the two study sites at the Estuary consists of metamorphic rocks such as granulite etc 
(UNEP, 2002).The relief of the riverbed leading to the Estuary as well as that of the surrounding 
areas of the Estuary is smooth with a very low gradient. Water depths, even at large distances from 
the coast are shallow. Figure 1, situates Sogakope on Ghana map which is represented by red point. 
It also clearly shows Sogakope map. 
26 
 
University of Ghana http://ugspace.ug.edu.gh
 
Figure 1: Map showing the location of Sogakope in the Volta Region in Ghana  
 
3.2.2 Climatology and Geology of Legon  
The second area which was the University of Ghana Research farm, Legon, locates in the Coastal 
Savannah agro-ecological zone of Ghana. The rainfall pattern of the study area is bi-modal and 
records a total annual rainfall of about 800 mm. The mayor season stretches from April to July. 
The minor season lies within August and October (Dowuona et al., 2012). The experimental site 
soil is described as an Alfisol (SSS, 1998). This soil can be compared to Adenta series which has 
27 
 
University of Ghana http://ugspace.ug.edu.gh
been classified as Typic Kandiustalf (Eze, 2008), using USDA classification system. The topsoil 
(20-30 cm) is sandy loam and is inherently poor in fertility.  
 
3.2.3 Geographical location of experimental field  
Two separate field experiments were carried out at Sogakope (Tordome), in the district of South-
Tongu and University of Ghana Research farm, Legon, in the Greater Accra Region, from August, 
2017 to March, 2018. The first experiment was conducted at farmer’s field in Tordome. It is about 
3 km from the Sogakope town. The experimental station is located on latitude 05.96836oN and 
longitude 000.59569°E with an elevation of 35 m. The site on which the study was conducted was 
previously cultivated to maize. The second trial was conducted at University of Ghana, Research 
farm, Legon which is located on latitude 5o 39’N and longitude 0° 11’ W. 
 
3.3 Materials  
Five onion varieties: ‘Dayo’ from East West Seeds, ‘Trophy’ and ‘Orient F1’ from Bejo Seeds, 
‘Red-creole’ from Technisem Seed Company, were evaluated alongside the commonly cultivated 
variety in Ghana “Bawku-Red” from local distributors. They were studied for their growth and 
yield performance based on morphological and agronomical measurements.  
 
3.4 Experimental design and treatments 
Randomized Complete Block Design (RCBD) was used as an experimental design at both sites 
with 5 treatments and 4 blocks. The varieties represent the treatments. Two blocks and two 
plots/units were separated by an alley of 1 m, respectively. Appendix 4 and 5, respectively show 
28 
 
University of Ghana http://ugspace.ug.edu.gh
the field trial and the experimental unit (plot) layout, they indicate number of plants and the 
harvested area. Treatments were defined as follows:  
 
T1: Dayo  
T2: Trophy 
T3: Bawku-Red 
T4: Red-Creole 
T5: Orient 
 
3.5 Soil analysis 
Soil is a support of plant and a reservoir of various nutrients which are needed by plant to survive. 
The analysis of soils was based on physical and chemical aspects. The experimental area was 
divided into 3 different homogenous units based on the visual observation. The surface litter was 
removed at the sampling spot. Soil were then sampled from the top to 15 cm of depth after 
harvesting. This was performed using a zig-zag pattern to ensure homogeneity. In total, 18 sub-
samples were collected from the entire experimental area. Then, six (6) sub-samples were collected 
from each sampling unit, place in a bucket and mix well. This was then transferred to a polythene 
bag (white) and labeled. After mixing, 3 representative samples were sent to laboratory for 
analysis. Analyses of soils was done for experiment one and two separately. It was carried out by 
the Soil Science Department (laboratory) at University of Ghana.  
 
29 
 
University of Ghana http://ugspace.ug.edu.gh
3.6 Cultural practices 
3.6.1 Land preparation   
After clearing of the area, plowing was done at a depth of 15 cm using a tractor followed by the 
leveling of the experimental area. The field was then prepared using cutlass and hoe. The 
experimental area of 23 x 9 m was measured out using a tape measure, garden line and pegs. The 
total land area for the study in each season was 207 m2 with a block size of 29 m2. Field plot of 5 
m x 1 m (5 m²) with 10 rows each 5 m long were prepared for this study. The distance between 
rows and plants were both 10 cm. Beds were raised to 15 cm high.  
 
3.6.2 Nursery preparation and transplanting 
Nursery beds were prepared using cutlass and hoe after ploughing. Beds were raised at 20 cm high 
and 10 m x 1 m. Further leveling was done manually with a rake for a fine and even seedbed. 
Before sowing the soil was watered to field capacity. For raising of seedling, onion seeds were 
sown on 17th July, 2017 on raised bed at Sogakope and 1st December, 2018 at Legon. Seeds were 
then sown by hand and covered with soil to a depth of 2 cm. A light irrigation was applied after 
sowing, using a watering cans. The nursery was covered with palm leaves to conserve moisture 
particularly at the surface and to avoid seeds being picked up by insects. The palm leaves were 
removed as soon as seed emergence began. The NPK 15:15:15 fertilizer were applied at a rate of 
50 g per 15 L of water using a knapsack sprayer, two weeks after sowing. Irrigation was done on 
a daily basis, except on days that it rained. After emergence, irrigation was done every second day 
until one month, after which onion seedlings were transplanted. 
 
30 
 
University of Ghana http://ugspace.ug.edu.gh
Four weeks after transplanting (11th August, 2017) or at three leaves stage at Sogakope and 3rd 
January, 2018 at Legon, the seedlings were transplanted to their respective plots. A seedling hole 
of about 3 cm of depth was filled with 1 seedling. The hole was closed immediately. Transplanting 
was done using a ‘Dybbar’ and the distance was 10 cm x 10 cm for a density of 500 plants/plot.  
 
3.6.3 Onion fertilization  
Prior to transplanting, 500g/plot of recommended NPK (15:15:15) fertilizer and 15 kg per plot of 
poultry manure were applied as basal fertilizer a day before transplanting. Three weeks after 
transplanting, 300g/plot of Sulphate of Ammonia was applied as top dressing.  
 
3.6.4 Onion irrigation 
The pipe method and watering cans were used for irrigating the onion crop respectively at 
Sogakope and Legon. The irrigation was carried out 3 times a week at Sogakope and daily at 
Legon. This irrigation frequencies were varied according to plant growth stages. Three weeks 
before harvesting, the plants were no longer irrigated. 
 
3.6.5 Onion weeding 
Weeding is the most important practices in agriculture. This need to be done properly in order to 
reduce nutrients, water and space competitions between crop and weed and to increase yield. Hand 
picking of weeds was carried out throughout the nursery stage of the onion crop. During the 
experiment, weeding was also done every 14 days starting from two weeks after transplanting 
(WAT) by hand picking. This was carried out three to five times depending on the experimental 
site. The dominant weed recorded in all the farms was Cyperus rotundus (nutgrass).  
31 
 
University of Ghana http://ugspace.ug.edu.gh
3.6.6 Pesticide application 
Fungal diseases were prevented by spraying Topsin M (Thiophamate methyl) at a rate of 70 g per 
15 liters of water. The application was done only once throughout the experiment. Then, Lamda 
halometry, was also used as an insecticide to prevent insects such as crickets at a rate of 2.5 cc per 
16 liters of water. 
 
3.6.7 Onion harvesting and curing 
‘Bawku-red’ and ‘Trophy’ varieties were harvested when 50% of the leaves were dried up. They 
were harvested one week before the other varieties; ‘Dayo’, ‘Red-creole’ and ‘Orient’. The 
harvested bulbs were dried in the sun light for two weeks. Two weeks after curing, the stem was 
cut using a grafting knife at one centimeter (1 cm) from the top of bulb. The hand fork was used 
to uproot onion bulb. 
 
3.7 Sample preparation 
To determine the characteristics and chemical contents of available nutrients in the soil, soil 
particles were in the suitable size (expressed by diameter) and dryness conditions.  The sample 
collected from the experimental area was dried in shade by spreading on a clean sheet of paper or 
newspaper after breaking the large lumps. The sample was then powdered by breaking the clods 
to its ultimate soil particle using a wooden mallet. The soil material was sieved through 2 mm 
sieve. Powdering and sieving were repeated until only coarse fragments (>2 mm) were left on the 
sieve. The material passing through the sieve was collected and stored in a clean glass or plastic 
container or polythene bag with proper labeling for laboratory analysis. In the case of organic 
matter determination, a representative sub sample was ground and sieved through 0.2 mm sieve.  
32 
 
University of Ghana http://ugspace.ug.edu.gh
3.8 Physical analysis 
3.8.1 Particle Size Distribution 
The soil fraction of 2 mm size or less was used. 2 mm soil size or less of sand, 0.05 mm or less of 
silt and less than 0.002 mm of clay fractions were estimated. Primary, particles were removed by 
means of water treatment. The hydrometer method recommended by Day (1965) was utilized to 
calculate the percentage of soil particle size. 40 g of 2 mm of dry soil was weighed in 600 ml jar. 
Then, 60 mL of dispersing solution was added and covered for a night. The content was changed 
to a stirring cup which was filled with water and stirred for 3 minutes.  
 
For Blank determination, 60 ml of the solution was mixed with water. This was diluted and shaken 
well. After inserting the hydrometer, Rb (blank) was read.  For Silt plus Clay determination, a new 
mixture was done with the suspension into the jar by means of a paddle which was removed after 
40 seconds. After inserting the hydrometer again, Rsc (Silt plus Clay) was read. For Clay 
determination, the solution was kindly abandoned. 4 hours after inserting the hydrometer, Rc 
(Clay) was read. For Sand determination, the suspension was filtered using a 50 mm sieve and the 
sieve was properly cleaned. The sand was then transferred to beaker which was dried together with 
the sand at 105°C. The percentages of these soil particles were determined, according to UAE 
University recommendation, as follows: 
100
Silt and Clay Percentage = (sc −  b) x  
(oven − dry)
 
100
Percentage of Clay = (c −  b) x  
(oven − dry)
 
33 
 
University of Ghana http://ugspace.ug.edu.gh
Percentage of Silt = [Silt (%) +  Clay weight]  −  [ Clay (%)] 
100
  Sand percentage = Sand weight x  
(Oven − dry) 
                                
Sand weight = [Beaker +  Sand] − [Beaker (g)] 
 
Where:  b = Rb; c = Rc; sc = Rsc 
 
3.8.2 Soil Texture 
After the determination of the soil particles percentages, sand, silt, and clay was classified using 
the USDA textural triangle (Appendix 6).  
 
3.8.3 Soil organic carbon 
In the detection of soil Organic Carbon a known weight of soil was heated with an excess volume 
of standard K2Cr2O7 in the presence of Con. H2SO4. The soil was slowly digested at the low 
temperature by the heat of dilution of H2SO4 and the organic carbon in the soil was thus oxidized 
to CO2. The highest temperature attained by the heat of dilution reaction produced with the addition 
of Con. H2SO
o
4 was approximately 12 C which was sufficient to oxidize the active forms of the 
soil organic carbon but not the more inert forms of carbon that may be present. Therefore, the 
determination of soil organic carbon followed the procedure below. 
a. Take 1 g of soil in a 500 mL conical flask. 
b. Add 10 mL of 1N K2Cr2O7 solution and shake to mix it. 
c. Then add 20 mL Con. H2SO4 and swirl the flask 2 or 3 times. 
34 
 
University of Ghana http://ugspace.ug.edu.gh
d. Allow the flask to stand for 30 minutes on an asbestos sheet for the reaction to complete.  
e. Pour 200 mL of water to the flask to dilute the suspension. Filter if it is expected that the 
end point of the titration is not to be clear. 
f. Add 10 mL of 85% H3PO4 and 1 mL of Diphenylamine indicator and back titrate the 
solution with 0.5 N Ferrous Ammonium Sulphate, till the colour flashes from violet 
through blue to bright green. H3PO4 gives sharper endpoint, by making 
the colour change, distinct through a flocculating effect. 
g. Note the volume of Ferrous Ammonium Sulphate. 
h. Carryout blank titration (without soil) in a similar manner. 
 Calculation: 
 % of Organic Carbon in Soil (R) is, 
 
 Where: 
W = Weight of Sample 
V1 = Blank Titre value 
V2 = Titre value of the Sample 
N = Normality of K2Cr2O7 (Here it is 1N) 
C = Correction Factor (1.334, 1.724) 
 
 
 
 
35 
 
University of Ghana http://ugspace.ug.edu.gh
3.9 Chemical analysis 
3.9.1 Soil reaction (pH- determination) 
Soil pH influences plant nutrients availability in the soil and their absorption. The pH was 
determined using the distilled water method (White, 1969). Air dried sample of 20 g and 20 ml 
distilled water were added into a glass meter, from a suspension. The suspension was stirred with 
a glass rod for one hour and thereafter allowed to stand for 30 minutes. A digital waterproof pH 
meter (pH tester 30) was used to determine the pH of the prepared suspensions after it has been 
calibrated with distilled water. The electrode of the pH meter was partly inserted into the settled 
suspension and the pH of the sample measured (Black, 1965). 
 
3.9.2 Electrical Conductivity (EC) 
E C measurements in saturated paste extracts are a relatively fast and accurate method to determine 
the concentration of soils salts content which has significant correlation with plant growth 
parameters. Electrical Conductivity of the sample was measured by adding 20 g of air – dried 
sample into a beaker and 20 ml distilled water. The suspension was stirred with a glass rod for one 
hour and allowed to settle for 30 minutes. The electrical conductivity meter was calibrated with 
distilled water. The conductivity electrode was inserted into the supernatant and EC reading was 
taken (Black, 1965). 
 
3.9.3 Determination of total nitrogen (N) in soil samples  
Nitrogen is an important element required for plant life in particular. The Kjeldahl method 
permitted the available nitrogen to be precisely determined. The method of determination involved 
36 
 
University of Ghana http://ugspace.ug.edu.gh
three successive phases which are: digestion, distillation and volumetric analysis. To determine 
total nitrogen, the procedure below was followed. 
a. Weigh 5 g soil into digestion flask. 
b. Add 5 g digestion mixture and 20 ml H2SO4 conc (conical). 
c. Put the flask on digestion board with electric heaters. 
Heat gradually; low at 10-30 minutes, then raise heating degree. 
d. After the end of fuming, the digestion is continued for 1 hour after the solution had 
cleared with white colour of digestion mixture. 
e. Transfer the sample to 250 ml volumetric flask, complete the volume with distilled Water. 
f. Put 20 ml H3BO3 in Erlenmeyer flask and 4 drops of the indicator. 
Put the flask so that the lower tip of the glass receiver tube is below the boric acid surface. 
g. Start running the cooling water in condenser 
h. Start boiling the water in the boilers. 
i. Put 25 ml of the sample in the funnel with distilled Water. Released ammonia is trapped in 
boric acid. 
j. Ammonia is titrated with HCL or H2SO4. At end point the green colour just disappears. 
 
 The following calculation was done to determine the multi equivalence of the acid participating 
in the process of ammonia assimilating during digestion, from the titre value. 
- Determination of blank: 
     Volume (V) of HCl = x mL 
V of NaOH = y mL 
V of HCl absorbed by NH3 = x – y = z mL 
37 
 
University of Ghana http://ugspace.ug.edu.gh
- Determination of sample: 
          Volume (V) of HCl = p mL 
V of NaOH = q mL 
V of HCl absorbed by NH3 in sample = p –q = t mL 
V of HCl absorbed for NH3 by sample = m – n = s mL 
Nitrogen weight in 5 g of Sample = v x 0.0014 g of N = u g of N 
This can also be calculated as follow: 
 
(Sample titration − Blank)x noramlity x 14 x dilution
𝑁 % 𝑖𝑛 𝑠𝑜𝑖𝑙 =  
sample weight
 
3.9.4 Determination of available phosphorus (P) in soil samples 
The method of sodium bicarbonate of Olsen et al. (1954) was used to determine the available 
phosphorus (P) in the study soil sample. The method is based on the use of the HCO -3 , CO
-3
3  and 
OH- in the pH 8.5, 0.5MNAHCO3 solution to decrease the solution concentrations of soluble Ca
2 
by precipitation as CaCO3 and soluble Al
3+ and Fe+3 by formation of Al and Fe oxyhydroxides, 
thus increasing P solubility. Therefore, 420 g commercial grade of sodium bicarbonate (NAHCO3) 
was dissolved in distilled water and made to a final volume of 10 L, to obtain Olsen P Extracting 
Solution (pH 8.5, 0.5MNAHCO3). A magnetic stirrer or electric mixer was used to dissolve the 
NAHCO3.  Then, the extracting solution pH was adjusted to 8.5 with 50% solution hydroxide.  
The procedure for the determination of available phosphorus (P) was as follow: 
 
38 
 
University of Ghana http://ugspace.ug.edu.gh
a. Weigh 1 g of soil into a 50 mL Erlenmeyer flask, tapping the scoop on the funnel or flask 
to remove all of the soil from the scoop. 
b. Add 20 mL of extracting solution to each flask and shake at 200 excursions per minute 
(epm) for 30 minutes at a room temperature at 24 to 27oC. 
c. If it is necessary to obtain a colorless filtrate, add 1 cm3 (200 mg) of charcoal (DARCO 
G60, J.T. Baker, Phillipburg, NJ) to each flask. 
d. Filter extracts through Whatman No. 42 filter paper or through a similar grade of paper. 
Refilter if extracts are not clear. 
e. Analyze for P by colorimetry or inductively coupled plasma emission spectroscopy using 
a blank and standards prepared in the Olsen P extracting solution.     
The formula below was used to calculate Available Phosphorus content. 
    
P
Olsen Extractable P (mg soil )
kg
mg 0.020 𝐿 𝑒𝑥𝑡𝑟𝑎𝑐𝑡 
= [ Concentration of P in Olsen extract, ] 𝑋[ ] 
L 0.001 𝑘𝑔 𝑠𝑜𝑖𝑙
 
 
3.9.5 Determination of total potassium (K) in soil samples 
Potassium (K) enhances disease resistance in plants by strengthening stalks and stems, contributes 
to a thicker cuticle (leaf surface layer) which guards against disease and water loss, controls the 
turgor pressure within plants to prevent wilting, and enhances fruit size, flavor, texture and 
development. The following procedure used the LaMotte garden soil test kit model EM, Code 
5934, to determine Potassium level in the study soil sample.  
39 
 
University of Ghana http://ugspace.ug.edu.gh
a. Fill test tube to line 7 with Potassium Extracting Solution. 
b. Use 0.5 g spoon to add four measures of soil sample to test tube. 
c. Cap and shake vigorously for one minute. 
d. Remove cap and allow soil to settle. 
e. Use a clean pipet to transfer the clear liquid to another clean test tube. Fill a second test 
tube to line 5 with the liquid.  
f. Add one potassium indicator tablet to the soil extract in the second tube. 
g. Cap and shake to dissolve the tablet. A purplish color will appear. 
h. Add potassium test solution, two drops at a time. Keep a running count of the drops used. 
Swirl the test tube after each addition to mix the contents. Stop adding drops when the color 
changes from purplish to blue. Record the total number of drops added.  
Then, the potassium end point color chart was used as a guide in reading this color change. The 
test result was also read from a table, to determine the Potassium level in soil which depends on 
the number of drops added.  
 
3.10 Data collection 
Data on vegetative growth and reproductive parameters, and yield and yield components at harvest 
were taken. 
 
3.10.1 Vegetative parameters 
Ten onion plants were chosen in order to take plant growth parameters. They were selected from 
the two central rows of each experimental unit. Data was taken every 14 days starting from the 
second week after transplanting when the bulbs were fully formed. According to the practice 
40 
 
University of Ghana http://ugspace.ug.edu.gh
recommended by POVD (2016) and Atta (2015). The onion plant ceases to grow at that stage 
(Bosekeng, 2012).  
 
3.10.1.1 Percentage crop establishment 
Four weeks after transplanting (WAT), crop establishment was estimated. The technique consisted 
of counting all the plants on each plot. The percentage crop establishment was then estimated: the 
number of established plants was divided by the entire number of seedlings transplanted and 
expressing it as a percentage. The formula is as follow: 
Percentage crop establishment = (Number of established plants/ Total number of seedlings 
transplanted) x 100 % (Akuamoah-Boateng, 2016). 
 
3.10.1.2 Plant height 
Plant height was taken on ten tagged plants starting from two weeks after transplanting until when 
the bulbs were fully formed. The measurement was taken from the base of plant to the tip of the 
highest leaf by means of a ruler. The mean plant height for each plot was determined. 
 
∑𝐇𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝 𝐩𝐥𝐚𝐧𝐭𝐬
𝐌𝐞𝐚𝐧 𝐩𝐥𝐚𝐧𝐭 𝐡𝐞𝐢𝐠𝐡𝐭 (𝐜𝐦)  =  
𝐍𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐩𝐥𝐚𝐧𝐭𝐬 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝
 
3.10.1.3 Number of Leaves per plant 
The number of active leaves were counted. This was done only on ten tagged plants during data 
collection, starting from two weeks after transplanting until when the bulbs were fully formed. The 
mean number of leaves per plant for each plot was determined. 
41 
 
University of Ghana http://ugspace.ug.edu.gh
∑𝐍𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐥𝐞𝐚𝐯𝐞𝐬 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝 𝐩𝐥𝐚𝐧𝐭𝐬
𝐌𝐞𝐚𝐧 𝐧𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐥𝐞𝐚𝐯𝐞𝐬 =  
𝐍𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐩𝐥𝐚𝐧𝐭𝐬 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝
 
3.10.1.4 Stem diameter 
3.10.2 Reproductive parameters 
The ten record plants from the two central rows per plot, for determination of vegetative growth 
parameters were also used for data collection on reproductive parameters. After harvesting, bulbs 
were cured and dried for 2 weeks.  
 
3.10.2.1 Bulb weight 
After harvesting, ten selected bulbs were weighed together, with an electronic weighing scale in 
order to obtain the fresh weight (Appendix 5). This was expressed in g/m2 and converted to t/ha, 
to estimate the appropriate yield of onion.  
 
3.10.2.2. Bulb length 
A Caliper was used to determine the bulb height for the ten record plants. The measurement was 
taken starting from the top point to the base of the bulb and the mean bulb length was calculated 
(Grant & Carter, 1997; Hasegawa et al., 2001). 
 
3.10.2.3 Bulb diameter 
The diameter of bulb was measured using a pair of digital Vernier calipers (Model STAINLESS 
HARDENED). This was measured from the largest site or part of the bulb, in order to obtain the 
42 
 
University of Ghana http://ugspace.ug.edu.gh
bulb circumference. This was then multiplied by π value (3.14) to obtain onion bulb diameter. The 
mean bulb diameter was then calculated. 
 
3.10.2.4 Bulb neck diameter 
The bulb neck was measured by using a caliper (Model STAINLESS HARDENED). The mean 
bulb neck diameter was then calculated. 
 
3.10.3 Bulb quality parameters 
The following factors were used as indices of bulb quality parameters: bulb color, bulb shape, bulb 
firmness, bulb sugar level and bulb shelf life. 
 
3.10.3.1 Bulb colour  
The bulb colour was identified by using a colour chart as a guide (Appendix 7).  
 
3.10.3.2 Bulb shape 
Bulb form was observed and classified using the instruction of Boyhan & Kelley (2008) (Appendix 
3). 
 
3.10.3.3 Bulb firmness 
Penetrometer (Model tr, 44 Lb x 50 Lb; 20 Kg x 200 gr) was used to determine onion bulb firmness, 
on two selected bulbs per treatment or variety. The penetrometer was introduced into the bulb 
around the largest circumference and the depth of penetration was recorded. The figure was 
43 
 
University of Ghana http://ugspace.ug.edu.gh
recorded after about 5 seconds, by the time the penetrometer stabilized. The mean of the two 
measurements was used for statistical analysis.  
 
3.10.3.4 Bulb sugar content 
Sugar level of onion bulb was tested two and four weeks after harvesting by using the refractometer 
(Model HI 96801; 0 to 85% Brix). Only two onion bulbs for each treatment were used to record 
bulb sugar level. The bulb substance was extracted and left on an exact place for the refractometer 
to display the figure. The figure was recorded after some few seconds about 5 seconds to allow the 
refractometer to stabilize.  
 
3.10.3.5 Bulb shelf life and storage 
Data was also collected on bulb shelf life every week up to one month in storage. Ten (10) 
randomly selected bulbs harvested from the net plot were used for the storage and shelf life 
treatments. Bulbs were packed on a table and stored per plot separately at room temperature 
(25°C). Each ten bulbs was weighed before the storage process started. There were replication 
among treatments. 
 
Thereafter, onions bulbs were weighed every 2 weeks starting from 2 weeks after harvesting to 
determine the shelf life of each cultivar in storage. This has been done twice and during one month. 
All unmarketable bulbs such as rotten, germinated bulbs, etc…were discarded and recorded, so 
that the rate of marketable bulbs infection can be minimized or avoided (Chung, 1989; Getahun et 
al., 2003 and Msuya et al., 2005). The final weight of bulbs recorded for the first 2 weeks was 
44 
 
University of Ghana http://ugspace.ug.edu.gh
compared to that of the last 2 weeks. The percentage of the healthy and rotten bulbs was calculated. 
Data on shelf life of bulbs ended after one month (visual appearance). 
 
3.10.4 Yield and yield components 
Onion bulbs yields were evaluated from ten selected bulbs from the harvested area (0.1m2). The 
ten record plants for vegetative growth parameters collection were also used for data collection on 
yield and yield components. 
 
3.10.4.1 Total bulb yield 
Bulb yield was estimated based on the weight of ten tagged bulbs harvested from the 2 middle 
rows per plot. This was also calculated using the formula below (Baba-Moussa et al., 2015). The 
value obtained was then converted into yield per hectare. 
 
W x 10.000
Y =  
𝐴 𝑋 10
Where: Y is onion yield, expressed in t/ha;  
             W is the weight of 10 onion bulbs per field pot expressed in kg.  
             A is the harvested area (0.1 m2) 
 
3.10.4.2 Rotten bulb yield 
 Rotten bulb (unmarketable bulb) yield was determined after separating the healthy bulbs 
(marketable bulb). The mean rotten bulb yield was calculated for each of the treatment.  
 
45 
 
University of Ghana http://ugspace.ug.edu.gh
∑𝐘𝐢𝐞𝐥𝐝 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝  𝐫𝐨𝐭𝐭𝐞𝐧 𝐛𝐮𝐥𝐛𝐬 
𝐌𝐞𝐚𝐧 𝐫𝐨𝐭𝐭𝐞𝐧 𝐛𝐮𝐥𝐛 𝐲𝐢𝐞𝐥𝐝 =  
𝐍𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝 𝐛𝐮𝐥𝐛𝐬 
 
 3.10.4.3 Healthy bulb yield 
Healthy bulb yield was determined after separating the rotten bulbs. The mean healthy bulb yield 
was calculated for each of the treatment. 
 
∑𝐘𝐢𝐞𝐥𝐝 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝  𝐡𝐞𝐚𝐥𝐭𝐡𝐲 𝐛𝐮𝐥𝐛𝐬 
𝐌𝐞𝐚𝐧 𝐡𝐞𝐚𝐥𝐭𝐡𝐲 𝐛𝐮𝐥𝐛 𝐲𝐢𝐞𝐥𝐝 =  
𝐍𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐬𝐞𝐥𝐞𝐜𝐭𝐞𝐝 𝐛𝐮𝐥𝐛𝐬 
 
3.11 Data analysis  
Data collected was analyzed using the analysis of variance (ANOVA) for randomized complete 
block design (RCBD) with the help of the GenStat 9th Edition Software. Means which differed 
significantly were compared using the Fisher’s Protected Least Significance Difference (LSD) at 
probability level of 5% of significance (P=0.05). 
  
46 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER FOUR 
4.0 RESULTS 
4.1 Climatic conditions during the experimental period 
Table 1 shows the meteorological data of the study sites from August - December 2017 and January 
– May 2018. The average monthly temperature over the experimental period ranged from 23oC to 
36oC. The average relative humidity varied from 63 % to 82 %. Generally, rainfall recorded was 
good during the vegetative stage of the crop, while the highest amount of rainfall was recorded in 
September. The highest number of rainy days was recorded in August at Sogakope during the trial 
period. At Legon, the amount of rainfall recorded was low during the onion crop growth phase.  
High amount of rainfall and number of rainy days was recorded in the month of May. 
 
Table 1: Weather data of the experimental area at Sogakope and Legon 
    
 Average Average monthly temperature (o C) Average relative 
Months monthly Max. Min.  Humidity (%) 
 
rainfall (mm) 
Sogakope 
August 103.8 (31) 32 23 78 
September 173.1 (21) 31 23 78 
October 106 (24) 33 24 76 
November 85.7 (27) 34 24 73 
December 48.4 (14) 36 25 63 
Legon 
January 11 (1) 32 23 78 
February 22 (2) 32 24 79 
March 57 (4) 32 24 79 
April 97 (6) 32 24 81 
May 131 (9) 31 23 82 
Source: https://www.worldweatheronline.com 
 
47 
 
University of Ghana http://ugspace.ug.edu.gh
4.2 Soil analysis 
Table 2 shows the chemical (N, P, K, EC, C, and pH) and physical (sand, silt, clay and texture) 
characteristics of the soil at the two experimental sites at Sogakope and Legon. From the table, the 
pH (H2O1:1) ranged from 6.33 to 6.57 at the two locations. The results showed that the soil at 
Sogakope was moderately acid and slightly acid at Legon (Table 2). Electrical Conductivity (EC) 
of the soil at Sogakope was 158.8 µs/cm-1 and that of Legon was 232.1 µs/cm-1. Table 2 again 
shows that total nitrogen at Sogakope was 0.07% and that of Legon was also 0.07%. Available 
phosphorus was 9.54 mg/kg for Sogakope while Legon soils recorded 80.7 mg/kg. Potassium also 
for Sogakope soil was 0.08 Cmol/kg and that of Legon soil was 0.44 Cmol/kg. The organic carbon 
(C) content of both soils at Sogakope and Legon were 0.62% and 0.50 % respectively. The Sand 
content of the soil ranged from 66.20 to 67.97 % for that of Sogakope and Legon experimental site 
respectively. The Silt content also of the soils ranged from 9.12 to 10.86 % and Clay content of 
the soils ranged from 18.33 to 22.92 %. Both soils in the two locations were sandy loam in texture. 
 
 
 
 
 
 
 
 
48 
 
University of Ghana http://ugspace.ug.edu.gh
Table 2: Physico-chemical properties of the experimental sites after harvesting at Sogakope and 
Legon 
Soil analytical data Sogakope Legon 
Chemical properties 
Total Nitrogen (%) 0.07 0.07 
Available Phosphorus (mg/kg) 9.54 80.7 
Exchangeable base (Cmol/kg) 0.08 0.44 
Organic carbon (%) 0.62 0.50 
Electrical conductivity (µs/cm-1) 158.8 232.1 
pH (H2O1:1) 6.33 6.57 
Physical properties 
% Sand 66.20 67.97 
% Silt 10.86 9.12 
% Clay 18.33 22.92 
Texture Sandy Loam Sandy Loam 
Source: Soil Science Laboratory, University of Ghana, Legon, 2018 
 
4.3 Vegetative parameters 
The performance of the five studied varieties was estimated by the determination of selected 
vegetative growth parameters. The parameters used as indices of vegetative growth were crop 
establishment, number of leaves per plant, plant height and stem diameter. Measurements were 
taken every two weeks starting four weeks after transplanting (WAT).   
 
4.3.1 Percentage Seedling Establishment  
Onion seedlings were transplanted 4 weeks after sowing. Percent seedling establishment was 
recorded at 4, 6 and 8 weeks after transplanting (WAT). Plant population at both 4 WAT and 6 
49 
 
University of Ghana http://ugspace.ug.edu.gh
WAT was 100%. The percentage establishment at 4 WAT and 6 WAT showed no significant (p < 
0.05) statistical differences among the treatments. However, at 8 WAT some seedlings died 
reducing the plant population, with Bawku red in Sogakope having significantly (p > 0.05) lower 
values for Orient. Red creole and Trophy got damaged in both experiments. Percent crop 
establishment ranged from about 99.4 - 99.9% at both locations. Dayo and Red-creole registered 
the highest crop establishment 4 WAT 99.4% - 99.9%; the lowest was recorded by Bawku-red 
(99.4%) at Sogakope. At Legon, Dayo and Bawku-red registered the highest crop establishment 
(100%) and the lowest was Red-creole (99.8%). There were no statistical differences among the 
varieties (Table 3). 
 
Table 3: Seedling establishment percentage of onion grown at Sogakope and Legon 
 Percentage seedling establishment 
Variety Sogakope Legon 
4 WAT 6 WAT 8 WAT 4 WAT 6 WAT 8 WAT 
Bawku Red 100.0 100.0 99.4 100.0 100.0 100.0 
Dayo 100.0 100.0 99.9 100.0 100.0 100.0 
Orient 100.0 100.0 99.8 100.0 100.0 99.9 
Red creole 100.0 100.0 99.9 100.0 100.0 99.8 
Trophy 100.0 100.0 99.6 100.0 100.0 99.9 
LSD (P ≤ 0.05) NS NS 0.39  NS NS NS 
 
50 
 
University of Ghana http://ugspace.ug.edu.gh
4.3.2 Number of Leaves per Plant  
The number of leaves per plant differed significantly among the varieties (Table 4). Data on 
number of leaves were taken at week 4, 6 and 8 after transplanting. The number of leaves increased 
from week 4 WAT to 6 WAT but decreased at 8 WAT at both Sogakope and Legon (Table 4). 
‘’Trophy’’ recorded the highest number of leaves (8) at Sogakope and Red-creole had the lowest 
(6 leaves) at 4 WAT (Table 4). At Legon, the highest number of leaves (4.0 leaves) were recorded 
by ‘’Bawku-red’’, ‘’Dayo’’, ‘’Orient’’ and ‘’Trophy’’, whiles ‘’Red-creole’’ had the lowest (3.0) 
number of leaves per plant.  At week 6, the maximum number of leaves per plant (9.0) were 
obtained by ‘’Bawku-red’’ and the lowest number of leaves (7.0) was recorded by ‘’Red-creole’’ 
at Sogakope while, ‘’Bawku-red’’ and ‘’Orient’’ produced the maximum number of leaves (7.0) 
at Legon while ‘’Red-creole’’, ‘’Dayo’’ and ‘’Trophy’’ had the lowest number of leaves (6.0). At 
week 8, ‘’Dayo’’, ‘’Orient’’ and ‘’Red-creole’’ recorded the highest number of leaves (6.0) per 
plant and ‘’Bawku-red’’ and ‘’Trophy’’ had the lowest number of leaves (3.0 and 5.0) at Sogakope 
(Table 4).  
 
Results from table 4 also indicate that Sogakope experiment was relatively better in terms of 
number of leaves per plant compared to the Legon experiment. The mean values for varieties 
(Table 4) depicted that onion varieties were significantly different with respect to number of leaves 
per plant at 4 weeks after transplanting, but there were no significant differences among varieties 
in plant number of leaves at 6 weeks after transplanting.  
 
 
 
 
51 
 
University of Ghana http://ugspace.ug.edu.gh
Table 4: Number of leaves per plant of onion crop at Sogakope and Legon  
 Number of leaves per plant 
Variety Sogakope  Legon  
4 WAT 6 WAT 8 WAT 4 WAT 6 WAT 8 WAT 
Bawku Red 7.0 b 9.0 3.0 4.0 b 7.0 7.0 b 
Dayo 7.0 b 8.0 6.0 4.0 b 6.0 5.0 a 
Orient 7.0 b 8.0 6.0 4.0 b 7.0 7.0 b 
Red creole 6.0 a 7.0 6.0 3.0 a 6.0 5.0 a 
Trophy 8.0 c 8.0 5.0 4.0 b 6.0 5.0 a 
LSD (P ≤ 0.05) 0.61  NS NS 0.35 0.59  0.90 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.3.3 Plant Height 
Table 5 indicates a significant (p<0.05) difference in plant height among the varieties. The highest 
plant height was recorded by Dayo (57.1 mm) and Trophy (57.1 mm) 4 WAT at Sogakope. While 
‘’Dayo’’ (28.9 mm) and ‘’Trophy’’ (28.6 mm) had the highest plant height at Legon followed by 
Orient (56.5 mm) at Sogakope at 4 weeks after transplanting. The lowest plant height were found 
in Bawku-red cultivar in both experiments with a plant height of (44.9 mm) and (20.7 mm) 
respectively (Table 4.5). At 6 week, the highest plant height was registered in Dayo cultivar with 
a plant height of (67.6 mm) and (52.5 mm) followed by Orient (63.7 mm) and (52.4 mm) 
respectively at Sogakope and Legon experiment. The smallest plants were found in Bawku-red 
variety in both experiments with a plant height of (47.1 mm) and (41.0 mm) respectively. At week 
8 plant height was not significantly different (p<0.05) among the varieties. The data indicate that 
plant height was higher in Red-creole (46.4 mm) and Orient (60.1 mm) at Sogakope, and Legon 
52 
 
University of Ghana http://ugspace.ug.edu.gh
respectively (Table 5), while Bawku-red (19.8 mm) recorded the lowest plant height at Sogakope 
and Trophy (39.6 mm) at Legon.  
 
Table 5: Plant height of onion grown at Sogakope and Legon 
 Plant height (mm) 
Variety Sogakope Legon 
4 WAT 6 WAT 8 WAT 4 WAT 6 WAT 8 WAT 
Bawku Red 44.9 a 47.1 a 19.8 a 20.7 a 41.0 a 42.2 
Dayo 57.1 b 67.6 c 45.7 c 28.9 b 52.5 b 43.9 
Orient 56.5 b 63.7 b 39.9 bc 27.8 b 52.4 b 60.1 
Red creole 45.8 a 62.0 b 46.4 c 22.8 a 51.6 b 53.6 
Trophy 57.1 b 62.4 b 33.1 b 28.6 b 52.1 b 39.6 
LSD (P ≤ 0.05) 4.60 3.76 10.7 2.97 2.18 NS  
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.3.4 Stem diameter 
Stem diameter was significantly different (p<0.05) among the varieties (Table 6).  The biggest 
stem diameter was observed in ‘’Trophy’’ (12.17 mm) and (6.14 mm) cultivar in both experiments 
followed by ‘’Dayo’’ (11.12 mm and 5.56 mm) at Sogakope and Legon respectively, at 4 WAT. 
Whereas the smallest stem diameter was observed in ‘’Red-creole’’ and ‘’Bawku-red’’ cultivars 
in both experiments with a plant stem diameter of (7.89 mm) and (3.77 mm) respectively (Table 
6). At 6 WAT, stem diameter was highest in ‘’Dayo’’ (22.36 mm) and (11.18 mm) followed by 
‘’Orient’’ (20.98 mm) at Sogakope while ‘’Red-creole’’ (17.16 mm) had the lowest diameter.  At 
Legon, the highest diameter was recorded by ‘’Dayo’’ (11.18 mm) followed by ‘’Trophy’’ (9.66 
53 
 
University of Ghana http://ugspace.ug.edu.gh
mm) while ‘’Bawku-red’’ (8.04 mm) had the lowest diameter. At Legon a similar trend was 
observed. At 8 WAT, the biggest plant stem were obtained in ‘’Orient’’ (13.59 mm) and (12.40 
mm) cultivar at Sogakope and Legon experiments followed by ‘’Dayo’’ (13.56 mm) and ‘’Bawku-
red’’ (9.76 mm) respectively. The smallest plants stem were found within ‘’Bawku-red’’ (5.62 
mm) and ‘’Trophy’’ (7.50 mm) varieties respectively at Sogakope and Legon. 
 
Table 6: Stem diameter of onion grown at Sogakope and Legon 
 Stem diameter (mm) 
Variety Sogakope Legon 
4 WAT 6 WAT 8 WAT 4 WAT 6 WAT 8 WAT 
Bawku Red 9.48 b 17.48 a 5.62 a 3.77 a 8.04 a 9.76 ab 
Dayo 11.12 c 22.36 c 13.56 b 5.56 c 11.18 c 7.91 a 
Orient 10.62 c 20.98 bc 13.59 b 4.43 b 9.04 ab 12.40 b 
Red creole 7.89 a 17.16 a 12.83 b  3.96 ab 8.58 ab 7.61 a 
Trophy 12.17 d 19.31 ab 10.60 b 6.14 d 9.66 b 7.50 a 
LSD (P ≤ 0.05) 1.02 2.22 4.81 0.51 1.26 3.03 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.4 Reproductive parameters 
The reproductive indices were bulb length, bulb neck, bulb diameter, average bulb weight, healthy 
bulb weight and rotten bulb weight.  
 
54 
 
University of Ghana http://ugspace.ug.edu.gh
4.4.1 Bulb length 
Table 7 shows no significant (p > 0.05) difference in bulb length among the onion varieties at 
Sogakope, but at Legon, significant (p < 0.05) differences were observed in bulb length among the 
different varieties. ‘’Trophy’’ had longest bulb length of 64.6 mm followed by ‘’Red-creole’’ (59.3 
mm) and ‘’Orient’’ (57.8 mm), while the smallest bulb length was registered by ‘’Bawku-red’’ (55 
mm) followed by ‘’Dayo’’ (56.6 mm) at Sogakope.  At Legon, the longest bulb length was 
obtained in ‘’Trophy’’ (52.3 mm) followed by ‘’Red-creole’’ (49.6 mm) and ‘’Dayo’’ (48.3 mm) 
while the smallest bulb length was from ‘’Bawku-red’’ local (36.7 mm) followed by ‘’Orient’’ 
(44. 6 mm).  
 
Table 7: Bulb length of varieties of onion grown at Sogakope and Legon 
Variety Bulb length (mm) 
Sogakope Legon 
Bawku-red 55.0 36.7 a 
Dayo 56.6 48.3 bc 
Orient 57.8 44.6 b 
Red-creole 59.3 49.6 cd 
Trophy 64.6 52.3 d 
LSD (P ≤ 0.05) NS 3.79  
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.4.2 Bulb and neck diameter 
There was no significant difference in bulb diameter among the different varieties in both 
Sogakope and Legon experiments (Table 8). At Sogakope, the biggest bulb diameter was obtained 
55 
 
University of Ghana http://ugspace.ug.edu.gh
in ‘’Orient’’ (55 mm) followed by ‘’Dayo’’ (53.7 mm) and ‘’Bawku-red’’ local (53.3 mm) while 
the least bulb diameter was obtained from ‘’Trophy’’ (51.6 mm) followed by ‘’Red-creole’’ (51.9 
mm). At legon, the biggest bulb diameter was obtained in ‘’Orient’’ (50.16 mm) followed by 
‘’Dayo’’ (46.82 mm) and ‘’Red-creole’’ (45.95 mm). The least bulb diameter was obtained from 
‘’Bawku-red’’ local (42.07 mm) followed by ‘’Trophy’’ (45.82 mm).  
 
The bulb neck of the onion cultivars was only evaluated in the Legon experiment. Table 8 indicates 
that there was significant difference in bulb neck diameter among the different varieties. 
‘’Trophy’’ produced bulbs with significantly thicker necks (13.09 mm) than bulbs of Orient (9.21 
mm), Red-creole (9.21 mm), Dayo (7.52 mm) and Bawku-red (1.86 mm). The thinnest necks (1.86 
mm) was recorded by ‘’Bawku-red’’. 
 
Table 8: Bulb neck and diameter of varieties of onion grown at Sogakope and Legon 
Variety Bulb diameter (mm)  
Sogakope Legon Neck diameter (mm) 
Bawku-red 53.3 42.07 1.86 a 
Dayo 53.7 46.82 7.52 b 
Orient 55.0 50.16 9.21 b 
Red-creole 51.9 45.95 9.21 b 
Trophy 51.6 45.82 13.09 c 
LSD (P ≤ 0.05) NS NS 2.70 
 
 
56 
 
University of Ghana http://ugspace.ug.edu.gh
4.4.3 Bulb weight  
There was no significant difference in bulb weight among the different varieties in the trial 
conducted at Sogakope, but there were significant differences among varieties in the Legon 
experiment (Table 9). The biggest bulb weight was obtained in ‘’Orient’’ (82.2 g) and (71.9 g) 
followed by ‘’Trophy’’ (81 g) and (60.5 g) and ‘’Dayo’’ (77.8 g) and (58.9 g) in both Sogakope 
and Legon experiments respectively. In the Sogakope experiment, the least bulb weight was 
obtained from ‘’Red-creole’’ (76 g) followed by ‘’Bawku-red’’ (77.4 g), whereas in Legon 
experiment, the least bulb weight was obtained in ‘’Bawku-red’’ local (46.4 g) followed by ‘’Red-
creole’’ (58 g).  
 
Table 9: Bulb size and bulb yield of onion varieties grown at Sogakope and Legon 
 Sogakope Legon 
Variety Average bulb weight (g) Average bulb weight (g) 
Bawku Red 77.4 46.4 a 
Dayo 77.8 58.9 ab 
Orient 82.2 71.9 c 
Red creole 76.0 58.0 ab 
Trophy 81.0 60.5 bc 
LSD (P ≤ 0.05) NS 12.9 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.4.4 Healthy bulb weight (marketable weight) 
There was no significant difference in the healthy bulb weight among the different varieties in 
Sogakope experiment but, in the Legon experiment, there was significant difference in healthy 
57 
 
University of Ghana http://ugspace.ug.edu.gh
bulb weight (Table 10).  At Sogakope, (table 10) the highest healthy bulb weight was produced by 
‘’Red-creole’’ (571 g), ‘’Orient’’ (531 g), ‘’Bawku-red’’ (496 g) and followed by ‘’Dayo’’ (427 
g), ‘’Trophy’’ (405 g) in that order. In Legon the experiment, the highest healthy bulb weight was 
produced by ‘’Orient’’ (533 g), ‘’Red-creole’’ (441 g), ‘’Trophy’’ (363 g) and followed by 
‘’Dayo’’ (338 g), ‘’Bawku-red’’ (314 g) in that order. 
 
Table 10: Bulb shelf life of onion varieties grown at Sogakope and Legon at 2 weeks after storage  
 Sogakope Legon 
Variety Healthy bulb weight (g) Healthy bulb weight (g) 
Bawku Red  496.0 314.0 a 
Dayo 427.0 338.0 a 
Orient 531.0 533.0 b 
Red creole 571.0 441.0 ab 
Trophy 405.0 363.0 a 
LSD (P ≤ 0.05)  NS 146.6 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.4.5 Rotten bulb weight (unmarketable weight) 
There were no significant (p > 0.05) differences in rotten bulb weight among the different varieties 
in both experiments. In Sogakope experiment, Table 11 shows that ‘’Dayo’’ had the maximum 
rotten bulb weight (249 g) followed by ‘’Bawku-red’’ (227 g), ‘’Trophy’’ (212 g) and least rotten 
cultivar was ‘’Red-creole’’ (121 g) and then ‘’Orient’’ (188 g). In Legon, ‘’Dayo’’ had maximum 
weight of rotten bulb (251 g) followed by ‘’Trophy’’ (242 g), ‘’Bawku-red’’ (150 g) and least 
rotten cultivar was ‘’Orient’’ (106 g) followed by ‘’Red-creole’’ (139 g) (Table 11). 
58 
 
University of Ghana http://ugspace.ug.edu.gh
Table 11: Onion bulb condition at 2 weeks after storage for onion cultivars grown at Sogakope 
and Legon 
 Sogakope Legon 
Variety Rotten bulb weight (g) Rotten bulb weight (g) 
Bawku Red  227.0 150.0 
Dayo 249.0 251.0 
Orient 188.0 106.0 
Red creole 121.0 139.0 
Trophy 212.0 242.0 
LSD (P ≤ 0.05)  NS NS 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.5 Bulb quality parameters  
Bulb color, bulb shape, bulb firmness and bulb sugar level were recorded to determine onion bulb 
quality. 
 
4.5.1 Bulb colour  
Bulb color was visually identified by using a colour chart as a guide (Appendix 3). Table 12 shows 
that ‘’Bawku-red’’ is dark maroon in colour, ‘‘Orient’’ maroon color and ‘‘Trophy’’ regatta color, 
while ‘’Dayo’’ and ‘‘Red-creole’’ were observed to be mulberry.  
 
 
 
59 
 
University of Ghana http://ugspace.ug.edu.gh
Table 12: Bulb colour of onion varieties grown at Sogakope and Legon  
Variety Bulb colour 
Bawku-red Dark maroon (red) 
Dayo Mulberry (red) 
Orient  Maroon (red) 
Red-creole Mulberry (red) 
Trophy Regatta (yellow) 
 
4.5.2 Bulb shape 
Bulb shape (Table 13) in the current work was visually identified. ‘Bawku-red’, ‘Red-creole’ and 
‘Orient’ produced thick flat bulbs, while ‘Dayo’ and ‘Trophy’ produced globe bulbs (Table 13).  
 
Table 13: Bulb shape of onion varieties grown at Sogakope and Legon 
Variety Bulb shape 
Bawku-red Thick flat 
Dayo Globe 
Orient  Thick flat 
Red-creole Thick flat 
Trophy Globe 
 
4.5.3 Bulb firmness 
In both experiments, onion bulb firmness was different depending on the variety, although the 
difference was not significant (Table 14). At Sogakope and Legon experiments, ‘Trophy’ bulbs 
were softer (17.75) and (17.20) than all the other cultivars followed by ‘Orient’ (15.62) and (14.28) 
at Sogakope and Legon respectively. The least bulb firmness was recorded by ‘Red-creole’ (12.90) 
60 
 
University of Ghana http://ugspace.ug.edu.gh
and (12.75) respectively at Sogakope and Legon. Results of this study showed that the onion bulbs 
from the first experiment which was conducted in 2017 at Sogakope, produced firmer bulbs than 
the second trial conducted at Legon, but the difference was not significant.  
 
Table 14: Bulb firmness of onion varieties grown at Sogakope and Legon 
  
 Firmness 
Variety 
  
Sogakope Legon 
Bawku red 13.32 12.88 
Dayo 13.47 12.97 
Orient 15.62 14.28 
Red creole 12.90 12.75 
Trophy 17.75 17.20 
LSD (P ≤ 0.05) NS NS 
 
4.5.4 Bulb sugar level 
The sugar content of onion bulbs was measured at 2 weeks and 4 weeks after harvesting in both 
experiment at Sogakope and Legon. ‘’Trophy’’ (11.45) recorded the highest sugar content 2 weeks 
after harvesting followed by ‘’Orient’’ (10.55) at Sogakope while ‘’Dayo’’ had the lowest, even 
though there was no significant difference among varieties (Table 15). In the Legon experiment, 
at two weeks after harvesting, there was no significant difference among varieties for the sugar 
content. The highest sugar content occurred in Orient cultivar with a sugar level of (14.28) 
followed by Bawku-red (13.00) and Trophy (11.57), while the lowest sugar content was found in 
Red-creole (9.40). Table 15 also shows that at 4 weeks after harvesting, the sugar content of Orient 
61 
 
University of Ghana http://ugspace.ug.edu.gh
(12.85) cultivar was significantly higher than the rest of the varieties, while Trophy (10.42) had 
the lowest sugar level content at Sogakope. At Legon, Bawku-red (14.93) cultivar had the highest 
sugar content than the other varieties, while the lowest sugar content was found in Trophy (7.38). 
 
Table 15: Sugar content of onion bulbs grown at Sogakope and Legon at 2 and 4 weeks after 
harvesting 
 Bulb sugar level 
 Sogakope Legon 
Variety     
Week 2 Week 4 Week 2 Week 4 
Bawku red 8.95 12.02 ab 13.00 bc 14.93 d 
Dayo 8.75 10.77 a 8.62 a 9.70 b 
Orient 10.55 12.85 b 14.28 c 13.20 c 
Red creole 9.15 10.52 a 9.40 a 10.53 b 
Trophy 11.45 10.42 a 11.57 b 7.38 a 
LSD (P ≤ 0.05) NS 1.71 1.76 1.24 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.5.5 Bulb shelf life 
Onion bulbs were stored at room temperature (25oC) two weeks (2 weeks) after harvesting and 
curing. Table 16 shows that Red-creole (121.0 g; 139.0 g), Orient (188.0 g; 106.0 g) and Bawku-
red (227.0 g; 150.0 g) had less rotten bulb weight, while Dayo (249.0 g; 251.0 g) and Trophy 
62 
 
University of Ghana http://ugspace.ug.edu.gh
(212.0 g; 242.0 g) gave higher rotten bulb weight respectively from Sogakope and Legon 
experiment, even though there was no significant difference in rotten bulb weight among onion 
varieties. 
 
Table 16: Bulb weight of onion varieties grown in Sogakope and Legon at 2 weeks after storage  
 Sogakope Legon 
Variety Healthy bulb Rotten bulb Healthy bulb Rotten bulb 
weight (g) weight (g) weight (g) weight (g) 
Bawku Red  496.0 227.0 314.0 a 150.0 
Dayo 427.0 249.0 338.0 a 251.0 
Orient 531.0 188.0 533.0 b 106.0 
Red creole 571.0 121.0 441.0 ab 139.0 
Trophy 405.0 212.0 363.0 a 242.0 
LSD (P ≤ 0.05)  NS NS 146.6 NS 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test. 
 
4.6 Yield and yield components 
Total bulb yield, average bulb yield, healthy bulb yield and rotten bulb yield were all used as 
indices of yield. 
 
4.6.1 Healthy and Rotten bulb yield 
With regards to yield, Table 17 indicates that the maximum healthy bulb yield ranged from Red-
creole (5.71 t/ha) followed by Orient (5.31 t/ha), Bawku-red (4.96 t/ha), and the minimum yield 
was produced from Trophy (4.05 t/ha) followed by Dayo (4.27 t/ha), although there was no 
63 
 
University of Ghana http://ugspace.ug.edu.gh
significant difference among varieties, at Sogakope. But Dayo gave the highest rotten bulb yield 
(2.49 t/ha) which was significantly higher than other varieties followed by Bawku-red (2.27 t/ha), 
Trophy (2.12 t/ha) and the lowest rotten bulb yield was produced by Red-creole (1.21 t/ha) 
followed by Orient (1.88 t/ha). At Legon however, there was significant difference in healthy bulb 
yield among different varieties. Highest healthy bulb yield was produced by Orient (5.33 t/ha) 
followed by Red-creole (4.41 t/ha), Trophy (3.63 t/ha), and the least yield was produced by Bawku-
red (3.14 t/ha) followed by Dayo (3.38 t/ha). However, even though the rotten bulb yield was not 
significantly different in the Legon experiment, the highest rotten bulb yield was produced by 
Dayo (2.51 t/ha) followed by Trophy (2.42 t/ha), Bawku-red (1.50 t/ha) and least rotten bulb yield 
was Orient (1.06 t/ha) followed by Red-creole (1.39 t/ha). 
 
Table 17: Healthy bulb and rotten bulb yield of varieties of onion grown at Sogakope and Legon 
 Sogakope Legon 
Variety Healthy bulbs Rotten bulbs Healthy bulbs Rotten bulbs 
yield (t/ha) yield (t/ha) yield (t/ha) yield (t/ha) 
Bawku Red 4.96 2.27 3.14 a 1.50 
Dayo 4.27 2.49 3.38 a 2.51 
Orient 5.31 1.88 5.33 b 1.06 
Red creole 5.71 1.21 4.41 ab 1.39 
Trophy 4.05 2.12 3.63 a 2.42 
LSD (P ≤ 0.05)  NS 1.51 1.46  NS 
 
4.6.2 Total bulb yield  
The table 18 shows that there was no significant difference in the bulb yield among the different 
varieties in the Sogakope experiment, but there was significant difference among the varieties in 
64 
 
University of Ghana http://ugspace.ug.edu.gh
the Legon experiment. Results showed that the yield of onion varieties ranged from 4.64 to 8.22 
t/ha in both experiments. The cultivar ‘Orient’ was considered as the most productive variety with 
its best yield of (8.22 t/ha) and (7.19 t/ha) at Sogakope and Legon respectively. In the second place 
was Trophy (8.1 t/ha) and (6.05 t/ha) and Dayo in the third place (7.78 t/ha) and (5.89 t/ha) 
respectively at Sogakope and Legon. In the fourth place came Bawku-red with (7.74 t/ha) and Red-
creole (5.8 t/ha) respectively at Sogakope and Legon. However, Red-creole and Bawku-red had 
the lowest yield of 7.6 and 4.64 t/ha respectively at Sogakope and Legon. 
 
Table 18: Total bulb yield of onion varieties at Sogakope and Legon 
 Sogakope Legon 
Variety Yield (t/ha) Yield (t/ha) 
Bawku-red 7.74 4.64 a 
Dayo 7.78 5.89 ab 
Orient 8.22 7.19 c 
Red-creole 7.60 5.80 ab 
Trophy 8.10 6.05 bc 
LSD (P ≤ 0.05) NS 1.30 
Means in the same colon followed by the same letter are not significantly different at 5% level 
according to LSD test 
 
4.7 Correlation analyses 
Table 19 shows that bulb yield had positive and non-significant correlation with number of leaves, 
plant height, stem diameter, bulb sugar content, rotten and healthy bulb weight. Whereas it had 
significant and strong significant positive association respectively with bulb length (0.50*) and 
average bulb weight (1.00**), bulb weight (1.00**) and bulb diameter (0.82**). 
65 
 
University of Ghana http://ugspace.ug.edu.gh
 
Table 20 indicates that bulb yield had positive and highly significant correlation with bulb length 
(1.00**), bulb neck (0.94**), bulb weight (0.60**), bulb firmness (1.00**) and plant height 
(0.59** and 0.63**). It also had positive and significant correlation with rotten bulb weight 
(0.55*). Table 20 again indicates that bulb yield had positive and non-significant correlation with 
bulb diameter, number of leaves, stem diameter and bulb sugar content. It had negative and non-
significant correlation with healthy bulb weight. 
66 
 
University of Ghana http://ugspace.ug.edu.gh
Table 19: Correlation analysis  
  ABW BL BD BW BF NL8 NL4 NL6 PH4 PH6 PH8 SD4 SD6 SD8 BSC2 BSC4 RBW4 HBW BY 
ABW -                   
BL 0.50*  -                  
BD 0.82** -0.03  -                 
BW 1.00** 0.50* 0.82**  -                
BF -0.05 -0.03 -0.07 -0.05  -               
NL8 0.06 -0.02 0.20 0.06 0.01  -              
NL4 0.18 0.32 0.00 0.18 0.63** -0.15  -             
NL6 0.18 -0.01 0.31 0.18 -0.08 0.26 0.11  -            
PH4 0.32 0.24 0.26 0.32 0.45* 0.43 0.56* 0.06  -           
PH6 0.08 0.27 0.03 0.08 0.03 0.69** 0.12 -0.09 0.60**  -          
PH8 0.19 0.14 0.24 0.19 -0.21 0.79** -0.31 -0.10 0.26 0.80**  -         
SD4 0.29 0.31 0.14 0.29 0.48* 0.06 0.82** 0.22 0.84** 0.29 -0.16  -        
SD6 0.14 -0.05 0.28 0.14 0.10 0.59** 0.27 0.38 0.73** 0.64** 0.41 0.55*  -       
SD8 0.01 0.10 0.08 0.01 -0.07 0.77** -0.18 -0.11 0.48* 0.74** 0.74** 0.09 0.44  -      
BSC2 0.35 0.20 0.31 0.35 0.63** 0.08 0.51* -0.05 0.40 0.04 0.01 0.38 -0.01 0.03  -     
BSC4 0.06 -0.22 0.16 0.06 0.22 -0.18 -0.15 -0.13 0.12 -0.29 -0.38 0.06 -0.11 -0.08 0.25  -    
RBW4 0.29 0.42 0.05 0.29 -0.17 0.00 0.23 0.42 0.30 0.11 -0.11 0.40 0.29 -0.08 -0.12 0.01  -   
HBW4 0.32 -0.02 0.34 0.32 -0.08 -0.06 -0.39 -0.31 -0.30 -0.19 0.16 -0.38 -0.34 -0.05 0.04 0.14 0.67**  -  
BY 1.00** 0.50* 0.82** 1.00** -0.05 0.06 0.18 0.18 0.32 0.08 0.19 0.29 0.14 0.01 0.35 0.06 0.29 0.32  - 
Note: *   Significant at 5% ,  **  Significant at 1%, ABW=average bulb weight, BL=bulb length, BD=bulb diameter, BW=bulb weight, 
BF=bulb firmness, NL8=number of leaves at week 8 after transplanting, NL4=number of leaves at week 4 after transplanting, 
NL6=number of leaves at week 6 after transplanting, PH4=plant height at week 4 after transplanting, PH6=plant height at week 6 after 
transplanting, PH8=plant height at week 8 after transplanting, SD4=stem diameter at week 4 after transplanting, SD6=stem diameter at 
week 6 after transplanting, SD8=stem diameter at week 8 after transplanting, BSC2=bulb sugar content at week 2 after curing, 
BSC4=bulb sugar content at week 4 after curing, RBW4=rotten bulb weight at week 4 after storage, HBW4=healthy bulb weight at 
week 4 after storage and BY=bulb yield 
       
67 
 
University of Ghana http://ugspace.ug.edu.gh
Table 20: Correlation analysis 
 ABW BH BD BW BF NL8 NL4 NL6 PH4 PH6 PH8 SD4 SD6 SD8 BSC2 BSC4 RBW4 HBW4 BY 
ABW -                   
BL 0.50*  -                  
BD 0.82** -0.03  -                 
BW 1.00** 0.50* 0.82**  -                
BF -0.05 -0.03 -0.07 -0.05  -               
NL8 0.06 -0.02 0.20 0.06 0.01  -              
NL4 0.18 0.32 0.00 0.18 0.63** -0.15  -             
NL6 0.18 -0.01 0.31 0.18 -0.08 0.26 0.11  -            
PH4 0.32 0.24 0.26 0.32 0.45* 0.43 0.56* 0.06  -           
PH6 0.08 0.27 0.03 0.08 0.03 0.69** 0.12 -0.09 0.60**  -          
PH8 0.19 0.14 0.24 0.19 -0.21 0.79** -0.31 -0.10 0.26 0.80**  -         
SD4 0.29 0.31 0.14 0.29 0.48* 0.06 0.82** 0.22 0.84** 0.29 -0.16  -        
SD6 0.14 -0.05 0.28 0.14 0.10 0.59** 0.27 0.38 0.73** 0.64** 0.41 0.55*  -       
SD8 0.01 0.10 0.08 0.01 -0.07 0.77** -0.18 -0.11 0.48* 0.74** 0.74** 0.09 0.44  -      
BSC2 0.35 0.20 0.31 0.35 0.63** 0.08 0.51* -0.05 0.40 0.04 0.01 0.38 -0.01 0.03  -     
BSC4 0.06 -0.22 0.16 0.06 0.22 -0.18 -0.15 -0.13 0.12 -0.29 -0.38 0.06 -0.11 -0.08 0.25  -    
RBW4 0.29 0.42 0.05 0.29 -0.17 0.00 0.23 0.42 0.30 0.11 -0.11 0.40 0.29 -0.08 -0.12 0.01  -   
HBW4 0.32 -0.02 0.34 0.32 -0.08 -0.06 -0.39 -0.31 -0.30 -0.19 0.16 -0.38 -0.34 -0.05 0.04 0.14 -0.67**  -  
BY 1.00** 0.50* 0.82** 1.00** -0.05 0.06 0.18 0.18 0.32 0.08 0.19 0.29 0.14 0.01 0.35 0.06 0.29 0.32  - 
Note: *   Significant at 5% ,  **  Significant at 1%, ABW=average bulb weight, BL=bulb length, BD=bulb diameter, BW=bulb weight, 
BF=bulb firmness, NL8=number of leaves at week 8 after transplanting, NL4=number of leaves at week 4 after transplanting, 
NL6=number of leaves at week 6 after transplanting, PH4=plant height at week 4 after transplanting, PH6=plant height at week 6 after 
transplanting, PH8=plant height at week 8 after transplanting, SD4=stem diameter at week 4 after transplanting, SD6=stem diameter at 
week 6 after transplanting, SD8=stem diameter at week 8 after transplanting, BSC2=bulb sugar content at week 2 after curing, 
BSC4=bulb sugar content at week 4 after curing, RBW4=rotten bulb weight at week 4 after storage, HBW4=healthy bulb weight at 
week 4 after storage and BY=bulb yield 
68 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER FIVE 
5.0 DISCUSSION 
5.1 Climatic conditions during the experimental period 
The Climatic data obtained during the experimental period showed high values for both the 
maximum temperature and relative humidity. They were extremely high and could have impact on 
plant growth and development.  In 2002, Khokar et al. obtained similar results and indicated that 
when temperature is above 30oC and more than 80% relative humidity, it causes reduction in onion 
yield. Temperature ranged between 18 - 22°C can facilitate vegetative growth, but will slow 
bulbing rate. In order for proper and faster bulbing to occur right from bulb initiation to harvesting, 
temperature range between 25 - 28°C is required (Comrie, 1997; SAKATA, 2014). According to 
USAID (2009) and Werer agricultural research center unpublished report (2012), the required 
temperatures during bulb formation range between 15 – 30oC. High temperatures have a strong 
impact on bulb formation (Brice et al., 1997). For instance, bulb maturation is very high in many 
areas in Tanzania, yet yields are very low as a result of small bulb sizes and an increase in the 
formation of doubles and splits due to high temperatures.  The performance and development of 
the onion plant at every phase of growth is primarily controlled by temperature (Ansari, 2007; 
Abu-Rayyan & Abu-Irmaileh, 2004 and Coolong & Randle, 2003). 
 
5.2 Soil analysis  
Results showed that the soil was moderately and slightly acidic (water pH 6.33 and 6.57). Indeed, 
the soil is neutral when their pH included of 6.5 to 7.5 (Baize, 2000). According to Bray & Kurtz 
(1945) the phosphorus assimilable rate (9 ppm) was close to the critical threshold (between 8 and 
10 ppm) and reveals the lower fertility of soil because it was inferior to 40 ppm. Furthermore, the 
69 
 
University of Ghana http://ugspace.ug.edu.gh
soil content of organic carbon and organic matter was low. The sum of exchangeable bases (0.08 
and 0.44 Cmeq/kg) was also low and less than the average level (5mol/kg) according to Malouhi 
(1997). In general, the field soil had low levels of minerals, hence their very low fertility level. 
 
5.3 Vegetative Growth parameters 
5.3.1 Percentage Crop Establishment  
Results indicated that the percentage crop establishment was high in both seasons. This was 
possible because of the regular watering and rainfall received during the first two weeks after 
transplanting the onion seedlings in both seasons. Good land preparation coupled with judicious 
use of both organic and inorganic fertilizers, as well as the use of good quality seeds resulted in a 
higher percentage crop establishment (Tweneboah, 2000). 
 
5.3.2 Number of Leaves per plant 
The number of leaves per plant differed statistically among the varieties used. The results are 
similar to reports by Boukary et al. (2012a) and Dwivedi et al. (2012), indicating that variations 
obtained in production of leaves, as well as leaf weight between varieties of onion may be 
attributed mainly to the cultivar. The environmental conditions such as rainfall, temperature 
photoperiod may also influence plant leaf production. This is in conformity with work done by 
Ijoyah et al. (2008) that environmental conditions in which plants grow contribute to the 
development of leaves. Similarly, Okporie & Ekpe (2008), added that since the leaves of onion 
plants are photoperiodic sensitive it makes the leaves respond to day length. According to 
Bosekeng (2012), the minimum or the base temperature required for leaf and leaf canopy growth 
is 6°C. However, at temperature values less than the required temperature the number of leaves 
70 
 
University of Ghana http://ugspace.ug.edu.gh
fail to increase. Relative leaf growth rate increases linearly with temperature up to 20°C. When 
temperature is further increased, plant growth rate will begin to start to dwindle and when 
temperatures hit above 26°C growth will completely cease. Furthermore, the high percentage crop 
establishment contributed to increase in leaf number per plant. Similar results was obtained by 
Rizk (1997), who reported that the high percentage crop establishment might have also contributed 
generally to enhanced crop growth and hence the high leaf number per plant. Weerasinghe et al. 
(1994) findings agree with the results obtained, they also indicated that when competition in plant 
is very high seedling leaf number is decreased significantly. The results showed that the 
augmentation of plant number of leaves does not depend on the fertilizer applied. This statement 
is in conformity with Sultana et al. (2014), who stated that the sole application of N had no 
substantial impact on leaf number. According to Ahmed et al. (2013), the Giza Red cultivars gave 
the highest average of leaf number per plant at both 90 and 120 days after transplanting. Addai 
and Anning (2015) and Tsitsia (2012) observed that the number of sprouts had an influence on the 
increase in leaf number. Furthermore, Addai and Anning (2015), indicated that when the leaf 
number and bulb number was high, the sprout number will also be high. Iannotti (2008) also 
indicated that when the number of leaves of an onion plant was high the bulb number at harvest 
will consequently be high. The same observation was also made by Perez et al. (1996). In a study 
conducted by Bhatt et al. (2007) to check the effects of date of sowing [i.e. 18 (D1) and 28 (D2) 
August, 7 (D3) and 17 September (D4)] on yields of onions, results showed that D1 and D2 
recorded significantly higher number of leaves at both 45 and 60 days after the sowing date, as 
well as at harvest compared to the later sowing dates. Abdelkader Abou Azoom et al. (2014), 
confirmed ‘YD’ cv. as having produced the greatest number (9.36) whereas minimum number of 
leaves/plant was noted in ‘Z6’ cv. whose plants produced a mean of 5.43 leaves/plant. By week 8 
71 
 
University of Ghana http://ugspace.ug.edu.gh
onion bulb was fully formed and the production of new leaves ceased. This was supported by 
Brewster (1994), who reported that when bulbing starts the production of new leaves ceases.  
 
5.3.3 Plant height  
Results indicated that plant height was significantly different among the varieties. Sogakope plants 
were observed to be taller than Legon plants. This is in conformity with the work of Mohanty and 
Prusti (2001), who reported differences in height of onion plants as due not only mainly to genetic 
factors but also to environmental factors especially temperature and photoperiod (Tesfay et al., 
2011). Comparable results were obtained by Ahmed et al. (2013), who reported that the genetic 
factors of the cutivars used might contribute to differences obtained in plant height. This is also in 
line with findings of Gemma et al. (2007) and Soleymani and Shahrajabian (2012). Abdelkader 
Abou Azoom et al. (2014), confirmed that the tallest plant was observed within the ‘MA’cultivar 
(76.95 cm) followed by ‘YD’ (70.55 cm) whereas the smallest most dwarf plant was found within 
‘Z6’, ‘G502’ and ‘BHP’ with a plant height of 42.61, 54.47 and 47.33 cm. Similar variability in 
plant height between varieties was observed on onion (Ibrahim, 2010; Trivedi and Dhumal., 2010). 
This may also be due to the high percentage crop establishment. The findings of this study are 
similar to those observed by Rizk (1997), who reported that the high percentage crop establishment 
might have also contributed generally to enhanced crop growth and hence the high plant height. 
The plant ceased growing as soon as they reached their maximum height. This was in partial 
agreement with Brewster (1994), who observed that at the start of bulbing, both the second and 
third leaves of onion plant tend to desiccate, however the 8 and above leaves then develop and this 
results in high height of the crop. According to Ahmed et al. (2013) again, the transplanting dates 
of onion seedlings had significant effects on plant height. He confirmed again that the highest 
72 
 
University of Ghana http://ugspace.ug.edu.gh
values on plant height resulted from transplanting seedlings on 15th November (early transplanting 
date). This was supported by Bosekeng (2012), who reported that when onion plants are sown 
early they have enough time to grow and develop. This results in the formation of bigger plants. 
 
Addai & Scott (2011) attributed plant height differences to onion bulb size. They confirmed that 
in onion production the bulbs which are larger produce the maximum vegetative growth. The 
average sized bulb produce the next highest vegetative growth and the smallest sized bulb produces 
the lowest vegetative growth. The larger bulb sized onions were again seen to have more 
carbohydrates, as well as other nutrients than both average and small sized bulbs. The results 
obtained agree with the findings made by Tsitsia (2012), who indicated that, taller onion plants, 
with higher leaf length are usually seen in those with larger bulbs. However, Fuseini (2012) also 
reported that highest vegetative growth is seen in medium bulbs, as compared to large and small 
bulbs. Addai and Anning (2015), in their work indicated that bulb sizes of 6.5-8.5 cm in diameter 
facilitated high growth as well as bulb yield, while bulbs sizes ranging from 2.5-3.5 cm in diameter 
did not facilitate high vegetative growth and bulb yield. Leaf number has been used as a great 
determinant of plant height which activates the process of bolting when temperature is low. 
Khokhar et al. (2007) stated that when 7 to 10 leaves are formed on an onion plant that is its 
sensitive plant size.  
 
5.3.4 Stem diameter 
Results of the current study indicated that wide variations in stem diameter was observed among 
onion cultivars. These were also due to the variation of climate. The new varieties are significantly 
bigger than the local one in terms of stem diameter. This may also be due to good rain occurring 
73 
 
University of Ghana http://ugspace.ug.edu.gh
during the Sogakope experiment. Hasegawa et al. (2005) obtained an increase of diameter of 
Arisaema ternatipartitum after addition of chitosan in cultural substrate. 
  
5.4 Reproductive parameters 
5.4.1 Bulb length 
The study showed that the length of onion bulbs was relatively high. Furthermore, the results 
indicated that the length of onion bulbs from all the accessions used in the experiment were higher 
than that of the local variety. The results also showed that bulb length from Sogakope experiment 
were far higher than those from Legon. Similarly, analogous data were obtained for diameter and 
height of bulb by Moulin et al. (2012) working on different varieties of melon, tomato, pepper and 
potato.  
 
On the contrary, it was indicated by Yadav et al. (2003) and Reddy (2005) that N fertilization 
increased the bulb length of onion. Yohannes et al. (2013), obtained the same results, reporting 
that N application at different rates showed a significant effect on the mean bulb length. He added 
that among the different levels of N evaluated, the maximum rate of 150 kg/ha N recorded the 
highest mean length of bulb which was 12% more than the control.  
 
5.4.2 Bulb neck and diameter 
The results of the study clearly indicated that among the varieties high number of green leaves 
resulted in big size of onion bulb. Singh et al. (1989) and Blay et al. (2006) obtained similar results 
and reported that the size of the green leaves or tops at the time of maturity, as well as the number 
of leaves affects the size of the onion bulbs formed. The findings in this study is in total agreement 
74 
 
University of Ghana http://ugspace.ug.edu.gh
with Addai and Anning (2015), who confirmed that highest number of bulbs are produced from 
plants from large bulbs, this he attributed to the numerous leaves such plants possessed. The 
outcome of this study showed that new varieties are far bigger than the local one. Similar finding 
was reported by Awuah et al. (2009); Alidu (2013), reported that Bawku Red produced smaller 
bulbs. According to Lancaster et al. (1996), the physiological processes form a huge part of 
regulating the bulb growth and development and determine the final bulb size. The physiological 
processes are much related to the thermal time it takes for bulbing to occur. Lacy and Roberts 
(1982) suggested that Fusarium basal-rot also reduces the size of bulbs produced by affected 
plants. According to Cramer (2003), date of sowing has an influence on the size of onion plants 
formed and this consequently affects the sizes of onion bulbs formed. 
 
On the contrary, it was indicated by Abdissa et al. (2011) that irrespective of the application rate 
of nitrogen fertilizer it increases the diameter of the bulb diameter by approximately 12%, as 
compared to applying no nitrogen. It was further reported by Mohammadi-Fatideh and 
Hassanpour-Asil (2012) that at a rate of 150 kg/ha, nitrogen fertilizer produced bigger bulb size. 
According to Soleymani & Shahrajabian (2012), levels of nitrogen in the soil had an effect on bulb 
size. Sinnadurai (1992), confirmed that the addition of phosphorus, nitrogen, as well as potassium 
to the soil had an effect on the size of onion bulbs at harvest. Also Hassan and Ayoub (1978) (cited 
by Nigussie et al., 2015) stated that to increase total yield and average size of onion bulbs, and to 
reduce the bolting percentage, the levels of nitrogen can be raised. Then, Mishu et al. (2013) 
reported that amounts of sulphur had an impact on bulb weight of onion.  
 
75 
 
University of Ghana http://ugspace.ug.edu.gh
The result of the study indicated that the onion bulb size neck is dependent on the bulb size. 
Therefore, thick, medium or thin size bulbs generated bulbs with thick, medium or thin necks 
respectively. According to Gautam et al. (2006), several works insisted on the existence of genetic 
difference between the varieties of onion in the diameter of the neck.  
 
5.4.3 Average bulb weight  
The outcome of the study showed that bulb and neck size influenced bulb weight. This is similar 
to the work of Addai and Anning (2015), who observed that the cluster of bulb weight, individual 
bulb weight, as well as the number of bulbs that are planted per plant at harvest is influenced by 
the size of bulb.  
 
On the contrary, Abdelkader Abou Azoom et al. (2014), reported different bulb weights from 
different varieties, ‘BHP’ cv. produced the biggest bulb of 155.02 g followed by MA (139.25 g) 
and KR (110.43 g), whereas ‘Z6’ cv. had the minimum weight of bulb (63.13 g). Similar result 
was observed on others varieties of onion (Mohanty and Prusti, 2001; Mohanthesh et al., 2008; 
Trivedi and Dhumal, 2010; Dwivedi et al., 2012) and garlic (Volk, 2009). Similarly, Bosekeng 
(2012), also confirmed that when onion plants are sown early, they tend to have a longer growth 
period which then results in the formation of larger bulbs.  
 
5.5 Bulb quality parameters 
5.5.1 Bulb color 
The present study indicated that the color of onion bulb may be cultivar related. The result is in 
line with research done by Bettson (1961), who indicated that most foreign cultivars have a lighter 
76 
 
University of Ghana http://ugspace.ug.edu.gh
coloration, which were not acceptable to the local population. This difference may also be obtained 
when the rule and principle of onion bulb curing are fully followed.  Similar finding was obtained 
by Advisory committee on vegetable crops (2017), who indicated that when onions are cured at a 
temperature of 24 to 32oC and at relative humidity of 80%, the best skin color develops.  
 
Onion bulb is the widely consumed part of the plant, that is why its characteristics interested 
several works which insisted on the existence of genetic difference between the varieties of onion 
in diameter of neck (Gautam et al., 2006), skin thickness (Boukary et al., 2012a), color of skin 
(Currah and Proctor, 1990) and adherence of skin (Ahmed et al., 2013). According to Anil (2008), 
five major loci (i.e. I, C, G, L and R) control the colour of onion bulb. Also, similar finding was 
obtained on onion from 18 genotypes in Spain (Rivera-Martinez et al., 2005), 10 genotypes in 
Bengladesh (Nilufar, 2009) and 21 ecotypes in Nigeria (Boukary et al., 2012b).  
 
5.5.2 Bulb shape 
The findings obtained from this study are similar to those observed by Bosekeng (2012), who 
stated that the variety of the onion affects the onion bulbs formed. Jilani & Ghaffoor (2003) and 
Hasegawa et al. (2001) noted that every onion variety has a specific bulb type. There are different 
bulbs forms such as flat, globe and sphere. Grant & Carter (1994) stated that bulb shape is 
influenced by plant population, as well as sowing date. According to them, the bulb shape index 
changed from 1.02 to 1.06, when the population of plants increased dramatically.  
 
77 
 
University of Ghana http://ugspace.ug.edu.gh
5.5.3 Bulb firmness 
Onions genetic makeup makes their cultivars differ from one another with regards to bulb firmness 
(Chope et al., 2006 and Larsen et al., 2009). Similar result was also obtained in this work indicating 
that bulbs firmness varied among onion cultivars during both seasons (Table 9). The result shows 
that the firmer variety had the highest rotten bulb weight. Gubb & MacTavish (2002) reported that 
humidity at bulb maturity increases rotten bulbs percentages in the field as well as in storage. The 
present study indicated that bulbs from Sogakope experiment where the trial was conducted during 
the rainy season, were more firm than those of Legon. This might support the idea of Bosekeng 
(2012), who reported that at bulb formation stage in onion plant requires excessive water to support 
new coming organs. In Australia, Chung (1989) reported similar result that the more bulbs absorb 
water the firmer they are. According to Larsen et al. (2009), irrigation and the size of the bulbs 
also influence bulb firmness. According to STARKE AYRES (2014), the curing process allows 
for development of scale leaf colour and firming of the bulbs. 
 
According to Gomez-Galindo et al. (2004) cell turgor increases as soon as water potential 
increases. This could result in firmer plant tissue. This suggests that the high fructan content of the 
MBL87-WOPL might have been responsible for it having the firmest scales. However, if this were 
the case we would likely see large decreases in firmness in this variety after eight weeks in storage 
due to the large weight loss, most of which is presumed to be water (Komochi, 1990). Cellulose, 
the 1, 4-β-D-glucan that gives rise to microfibrils, is also generally thought to give the cell wall 
much of its strength (Carptia and Gilbeaut, 1993). The concentrations of cellulose were higher in 
MBL87-WOPL line than in Pegasus. Similarly, O’Donoghue et al., (2004) found that Pukekohe 
78 
 
University of Ghana http://ugspace.ug.edu.gh
Longkeeper, a firm long-storing onion, had higher concentrations of cellulose than a softer poor-
storing Houston Grano bulb. This suggests that cellulose may also be linked to firmness in onion. 
Recently, O’Donoghue et al. (2004) reported high concentrations of hemicellulose as well as 
cellulose in a firm, long-storing cultivar, Pukekohe Longkeeper, and low levels of cellulose and 
hemicellulose in a soft, short-storing cultivar, Houston Grano. Their results suggest that cellulose 
and pectin concentrations may be linked to bulb firmness. In addition to structural carbohydrates, 
the activity of cell wall modifying enzymes, polygalacturonase (PGA) and pectin methylesterase 
(PME) may affect onion firmness. The activities of PME and PGA are well correlated with 
softening in a number fruits and vegetables during the ripening process (Gomez-Galindo, 2004; 
Micheli, 2001). Although neither enzyme has been thoroughly experimented in onion, PGA 
activity was linked with diminution of cellular adhesion in Leek (Allium porrum L.), a close 
relative of onion (Peretto et al., 1992). In addition, Garcia et al., (2002) indicated the role of PME 
in onion tissue. Although other enzymes such as expansin, played an important role in fruits and 
vegetables softness (Brummell, 2006; Brummell and Harpster, 2004; Smith et al., 1990), the role 
of PME and PGA in relation to onion firmness has yet to be defined. However, PME and PGA 
have previously been detected in Allium species and it is reported that they act in onion pectin 
metabolism during storage.  
 
According to Coolong (2007), the firmness in onion at harvest may be linked to the concentration 
of cellulose and pectin in the bulb. Other factors, such as expansin activity may also be responsible 
for softening during onion storage. The author confirmed that firmness in onion scales may be the 
result of several factors. One may be the concentration of pectin and cellulose in onions. Pegasus 
contained low concentration of pectin as well as cellulose and was softer than others. MBL87-
79 
 
University of Ghana http://ugspace.ug.edu.gh
WOPL variety contained more of structural carbohydrates which made it firmer than the previous. 
The MSU4535 bulbs had intermediate levels of pectin and cellulose as well as firmness at harvest. 
A second factor related to bulb firmness in these lines may be the activity of PME and PGA. Both 
Pegasus and MSU4535B had higher PME and PGA activities and experienced their largest 
decrease in firmness relatively early during the storage period. The activities of PME as well as 
PGA in MBL87-WOPL were low at storage and softening was delayed until 8-12 weeks in storage. 
In addition, PME, which acts prior to PGA in cell wall disassembly peaked in activity in Pegasus 
and MSU4535B four weeks prior to the maximum observed PGA activity indicating that both 
enzymes may act together in the Pegasus and MSU4535B cultivars.  
 
According to Mallor et al. (2011), bulb firmness influenced the storability of onions. Lancaster et 
al. (2001a) and El-Tantawy & El-Beik (2009) respectively reported that sulphur or copper  affected 
onion bulb firmness. This was supported by Nasreen et al. (2003) who indicated that sulphur or 
copper fertilizers play a role of onion dry matter accumulation, strength bulb cells and increase 
onion bulb shelf life so that they can be stored long. In addition, low application of sulphur initiates 
softer bulbs (Lancaster et al., 2001b). Similar finding was reported by Grauert (2014), that N-
reduction does not lead to less yield but improved quality (skins, firmness etc.). 
 
5.5.4 Bulb sugar content 
Results of this work indicated that onion bulbs sugar content varied among onion varieties. It is 
also crucial to note that bulbs sugar content increased when storage temperature increased. But 
this may not be true with ‘Trophy’ cultivar where the sugar level content of onion bulbs decreased 
when the temperature of onion bulbs storage increased. In general, this study indicated that 
80 
 
University of Ghana http://ugspace.ug.edu.gh
‘Orient’ followed by ‘Bawku-red’ varieties contained more sugar than the other cultivars, while 
the lowest sugar content cultivar was observed in ‘Dayo’ followed by ‘Trophy’. Similarly, 
Benkeblia et al. (2002), indicated that storage temperature has impact on onion bulb sugar content. 
The bulb sugar content increased with increase in storage temperature. They added that variation 
of bulbs sugar content is affected by storage temperature. Hurst et al. in 1985 obtained similar 
results like that of Benkeblia et al. (2002).  
 
5.5.5 Bulb shelf life 
Results indicated that Red creole, Orient and Bawku-red onion have long shelf life, while Dayo 
onion has average shelf life and Trophy onion has short shelf life. This can be due to the variation 
in cultivars, physiological maturity, conditions of curing and storage. Similar finding was obtained 
by Hygrotech, (2009a & b), who reported that dry matter content and dormancy are some of the 
genetic factors which affect bulb shelf life. He added that photoperiod in bulb storage indicate 
whether bulb can be stored longer or shorter. He reported again that intermediate day cultivars (6-
7 months) store better than short day cultivars (4 months). According to Galvan et al. (1997), 
onions bulbs sown earlier have enough time to grow well, to produce large leaves. Large leaf areas 
effectuate better photosynthesis and accumulate enough assimilates for the plant to complete well 
its life cycle and the bulbs to be well stored. Bosekeng (2012) indicated that harvesting onions 
bulbs too early may cause lack of growth inhibitors translocation to onion bulbs. 
 
Wright & Grant (1997) reported that curing consists of drying harvested onion bulbs roots, outer 
skins and neck. According to them, the outer skins protect onion bulbs against postharvest 
pathogens during handling and storage. In addition, this postharvest practice increases bulbs shelf 
81 
 
University of Ghana http://ugspace.ug.edu.gh
life and reduces all types of bulb infection. The percentage of weight loss is minimized with long 
shelf life cultivars and maximized with short shelf life cultivars. Ramin (1999), observed that the 
loss of bulb water content can be reduced with 65 to 75% relative humidity when stored. Onion 
bulb shelf life and storage ability of a particular cultivar are very essential for onion growers so 
that they can stock onions until there is a shortage or lack of onion on the market (Joubert, 1997). 
Bulbs shelf life and storage depend also on it firmness, because firmer bulbs store better than softer 
bulbs (NAD, 2009).  
 
 5.6 Yield and yield components 
5.6.1 Total, Marketable and Unmarketable bulb yield  
Results showed that bulb yield and quality variations depended on onion cultivars. These were 
also affected by the type of climate. The results are in partial agreement with the findings of Jilani 
and Ghafoor, (2003); Kimani et al. (1993). According to them, the performance of a cultivar 
depends more on the interaction of genetic aspect of plant and specific environment. The results 
of this work is similar to that of Soleymani and Shahrajabian (2012), who stated that total yield 
was significantly influenced by cultivars.  Similarly, Abdelkader Abou Azoom et al. (2014) 
showed that the yield of onion varieties ranged from 15.42 to 36.88 t/ha and that some foreign 
varieties had slightly higher yield than that of the commercial variety ‘BHP’. According to them, 
these finding agreed with the results of other researches on onion in India (Mahanthesh et al., 
2008), in Canada (Best, 2000), in Burkina Faso (Rouamba et al., 2001), in Cote d’Ivoire (Silue et 
al., 2003), in Nigeria (Kabura et al. 2008; Ibrahim, 2010). These findings confirm that onion 
varieties have impact on bulb quality which affects the marketable yield (healthy yield) of onions. 
These observations are consistent with the results of the present work for total onion weight and 
82 
 
University of Ghana http://ugspace.ug.edu.gh
marketable or unmarketable yield. Bettson (1961) conducted experiments to compare the 'Bawku' 
variety with foreign cultivars and reported that foreign cultivars performed significantly better than 
the 'Bawku' in the Bawku District and recommended some foreign cultivars to farmers. The 
recorded variations among varieties in marketable yield could be due to their differences in genetic 
make-up and/or agro ecological adaptations. According to Sinnadurai and Abu (1977), the yield is 
very much dependent on the climate during the growing season and thus is very unpredictable. 
They added that the low yield may also be an inherent character since no selections were made for 
bulb size and colour. Ali et al. (2007) reported that lack of good quality seeds and selected varieties 
caused low onion yields. Shaikh et al. (2002), confirmed that the use of good seed increased onion 
yield up to 30%.  Ali et al. (2007) reported that when soil is too wet onion yield can be affected. 
In Botswana, Baliyan and Kgathi (2009) reported that poor yielding varieties, severe climate and 
poor soils contribute to low productivity of vegetables such as onion. Tarpaga et al. (2011) reported 
that the yield of onions depends on climatic conditions. Wiles (2006) and Baliyan (2014) indicated 
that good management and agronomic practices, new varieties and available onion varieties 
ameliorate onion yield.   
 
Composition of crop media such as soil (Suthamathy and Seran, 2011), planting date (Hamma, 
2013; Mitiku et al., 2017), and other differences in cultural practices could also be the origin of 
variations in yield especially irrigation (Biswas et al., 2010). Khokar et al. (2002), reported that 
when the maximum temperature is higher than 30°C and the relative humidity is also higher than 
80%, onion yield is reduced drastically. The outcome of this current work is similar to that of 
Khokar et al. (2002). The results showed that harvest time may also affect negatively onion bulb 
83 
 
University of Ghana http://ugspace.ug.edu.gh
yield and quality. This is in agreement with the work of Boyette et al., (2008), who reported that 
onion bulbs yield and quality decreased when harvested at 10% - 20% top fall. 
 
On the contrary, Fuseini (2012), reported that the application of high rate of fertilizer (250 kg/ha) 
provided the maximum bulb number. He added that the number of bulb produced by plant depends 
on the percentage of phosphorus found in the soil. This findings of Fuseini confirmed that of 
Nagaraju et al. (2000) who reported that the higher percentage of P produced the high bulb number. 
But, It has also been reported that, application of high rate of nitrogen (more 84 kg/ha) had impact 
on crop yield (Wiedenfeld, 1994). Addai and Anning (2015) reported that the application of NPK 
at highest rate than 80 kg/ha reduced bulbs yield considerably.  
 
5.6.2 Yield comparison between Sogakope yield and Legon 
Table 18 shows the bulb yield in the Sogakope experiment and Legon, even though the 
experimental period was not the same. When the bulb yields are compared there were differences. 
These differences may have resulted from the observation that the weather in Legon was not 
favorable enough. In 2018 (Legon), lots of heavy rains prevailed during the cropping season. 
Subsequently, during the bulb formation, the temperature and the number of rainy days were low 
and the relative humidity also, not usual than the previous year (2017), was high so the result has 
gone down ultimately. The experiment at Sogakope (2017) showed 8.22 t/ha of yield, even though 
there were no significant difference among the varieties and that of Legon (2018) was 7.19 t/ha, 
there were significant difference among varieties. The performance is shown in the table 18 to 
check the yield of this year and last yield results for the best variety. 
 
84 
 
University of Ghana http://ugspace.ug.edu.gh
5.7 Correlation analyses 
The results showed that bulb yield had positive as well as non-significant association with number 
of leaves, plant height, stem diameter, bulb sugar content, rotten as well as healthy bulb weight. 
Whereas it had negative and non-significant correlation with bulb firmness. Bulb yield again had 
significant and strong significant positive association respectively with bulb length and bulb 
average weight, bulb weight and bulb diameter. This is similar to the work of Akuamoah-Boateng 
(2016) who reported that total onion bulb yield had positive as well as highly significant 
association with bulb diameter, bulb length, leaf diameter, mean bulb weight, number of leaves 
and plant height.  Rahman and Das (1985) reported similar association in garlic and Islam et al. 
(2007) in onion. Clearly, bulb yield had positive and highly significant association with plant 
height, number of leaves, root numbers and root length per plant. They added that the yield increase 
as the root number increase. While leaf number has negligible impact on yield improvement. In 
addition, root length has no effect on bulb yield increase (Rahman and Das, 1985 and Islam et al. 
2007).  
 
 
 
 
 
 
 
 
 
85 
 
University of Ghana http://ugspace.ug.edu.gh
CHAPTER SIX 
6.0 CONCLUSIONS AND RECOMMENDATIONS 
6.1 Conclusions 
Two field trials were carried out to evaluate the yield performance of four varieties of onion against 
the commonly grown variety ‘Bawku-Red’ under two different ecozones (Sogakope and Legon). 
The four onion varieties, were Dayo, Trophy, Red-Creole, and Orient. The results indicated that 
Orient was the best performing onion variety as it produced the highest yield of 8.22 t/ha and 7.19 
t/ha followed by Trophy (8.10 t/ha and 6.05 t/ha) at Sogakope and Legon respectively. Based on 
varietal characteristics of vegetative performance, bulb shape, bulb color, bulb firmness, bulb 
sugar level, bulb size, good yield, easy availability of seeds and cheaper price of seeds in the local 
market, Orient was the best variety followed by Trophy at both sites.  
 
6.2 Recommendations 
 Trophy onion can be recommended for the fresh market, but not for storage because of its 
high unmarketable or low marketable yield and short shelf life.  
 
 For distant markets where dry, cured bulbs are in demand, Orient is recommended since it 
has a long shelf life.  
 
 These varieties may be evaluated again with Bawku red to ascertain their performance 
under field conditions.  
 
 Orient followed by Trophy cultivar should be promoted for cultivation in Southern sector.  
86 
 
University of Ghana http://ugspace.ug.edu.gh
 The Ministry of Food and Agriculture (MoFA) along with the potential farmers across the 
country should provide effective platform for development and adoption of Orient and 
Trophy onion cultivars.  
 
 It is recommended that further investigation on the yield performance of the varieties be 
evaluated across other locations especially in the Northern and Upper Regions with varied 
ecology in Ghana. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
87 
 
University of Ghana http://ugspace.ug.edu.gh
REFERENCES 
Abdelkader Abou Azoom, A., Kaouther, Z., & Cherif, H. (2014). Performance of eight varieties 
of onion (Allium cepa L.) cultivated under open field in Tunisia. Sousse University, 
Department of Horticulture and Landscape, Higher Institute of Agronomy, 4042, Chott 
Mariem, Tunisia. Available from: www.notulaebiologicae.ro, Not sci biol, 6(2): 220-224 
Abdissa, Y., Tekalign, T. & 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. Afr. J. Agric. Res., 6: 3252-3258. 
Abu-Rayyan, A.M. & 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. Accra, 
Ghana. 
Addai, I.K. & Anning, D.K. (2015). Response of Onion (Allium cepa L.) to Bulb Size at Planting 
and NPK 15:15:15 Fertilizer Application Rate in the Guinea Savannah Agroecology of 
Ghana. Journal of Agronomy 14 (4): 304-309, DOI: 10.3923/ja.2015.304.309 
Addai, I.K., Takyi, H. & Tsitsia, R.K. (2014). Effects of cultivar and bulb size on growth and 
bulb yield of onion (Allium cepa L.) in the Northern Region of Ghana. British Journal of 
Applied Science & Technology, 4(14): 2090-2099 
Addai, I.K. & Scott, P. (2011). Influence of bulb sizes at planting on growth and development of 
the common hyacinth and the lily. Agric. Biol. J. North Am. 2: 298-314. 
Ado, P.O. (2001). Onion cultivation. Onion Newsletter, 20: 30-34.  
Adomako, P. (1959). Onion cultivation in Kusasi. Ghana Farmer 3(4):129-131, 142. 
88 
 
University of Ghana http://ugspace.ug.edu.gh
Adongo, B. A., Kwoseh, C. K. & Moses, E. (2015). Storage rot fungi and seed-borne pathogens 
of onion. Journal of Science and Technology, Vol. 35, No. 2, 13-21. 
http://dx.doi.org/10.4314/just.v35i2.2. 
Advisory Committee on Vegetable Crops (2017). Onions: Vegetable crops production guide for 
the Atlantic Provinces. Published by authority of the Atlantic Provinces Agriculture 
Services co-ordinating committee, Canada, p.8 
Ahmed, A.K., Ali, E.S., & Fathalla, H.F. (2013). Effect of transplanting dates of some onion 
cultivars on vegetable growth, bulb yield and its quality, Egypt. ESci Journal of Crop 
Production, 02 (03). 72-82. 
Akhtar Ehsan, M., Khurran, B., Khan, M. Z., & Khakhar, K. M. (2002). Effect of potash 
application on yield of different varieties of onion (Allium cepa L.). Asian J. of Plant Sci., 
1 (4): 324-325.  
Akrofi, S., Kotey, D.A., Ahiatsi, E.N., & Larbi-Koranteng, S. (2016). Onion Farming Practices 
in Eastern Region of Ghana: Implications for Research. Asian Journal of Agriculture and 
Food Sciences, Volume 04 – Issue 04, p. 13 (Available from: www.ajouronline.com)  
Akuamoah-Boateng, M. (2016). Effect of poultry manure and NPK fertilizer on the growth, yield 
and mineral composition of onion (Allium cepa L.) grown in acid soil, MPhil Thesis, Crop 
Science Department, University of Ghana, Legon, p. 153. 
Ali, M. K., Alam, M. F., Alam, M. N., Islam, M. S. & Khandaker, S. M. A. T. (2007). Effect 
of Nitrogen and Potassium level on yield and quality of seed production of onion. J. Appl. 
Sci. Res. 3:1889-1899.  
89 
 
University of Ghana http://ugspace.ug.edu.gh
Alidu, A.I.  (2013). Etiology and control of bulb rot disease of onion (Allium cepa L.) in the 
Eastern region of Ghana, MPhil Thesis, Department of Crop Science, University of Ghana, 
Legon, p. 106 
All About Onions (https://www.onions-usa.org/all-about-onions/history-of-onions). US National 
Onion Association, Greeley, CO. (2018). Retrieved 15/05/2018. 
Anil, K. (2008). Segregation for onion bulb colors reveal that red is controlled by at least three 
loci. J Am Soc Hort Sci 133:42-47. 
Anne McCabe, Mick O'Donnell, & Rachel Whittaker (2007). Advances in Language and 
Education. Bloomsbury Publishing. p. 35. ISBN 9781441104588 
Anonymous (2005). National Onion Association. http://www.onionsusa. 
org/about/production.asp. (Accessed 27/2/2012). 
Ansari, N.A. (2007). Effect of density, cultivars and sowing date on onion sets production. Asian 
J. Plant Sci. 6, 1147-1150. 
Arris Pty Ltd. www.arris.com.au : 05-Jun-18; 4:49 PM 
Assibey-Yeboah, S. (2018). Deputy Programme Leader of GhanaVeg, speaking to stakeholders 
at a trial field event at Legon 
Atta, M. (2015). Response of maize (zea mays L.) crop to biofertilization with plant growth 
promoting rhizobacteria and chitosan under field conditions. Thesis, Master of Agriculture 
in Crop Science, Department of Agronomy, University of Gasa-Formation (UATM), Benin. 
pp.79 
Awuah, R. T., Kwoseh, C., Koranteng, S. L., Okpala, R.O.C., & Amoako–Attah, I. (2009). 
Appearance of Fusarium basal rot of onion in the Kwahu South District of Ghana. Ghana 
J. Hortic., vol 7, 84 – 88. 
90 
 
University of Ghana http://ugspace.ug.edu.gh
Baba-Moussa, L., Agbodjato, A. N., Noumavo, A. P., Atta, M., Adjanohoun, A., 
Dagbenonbakin, G., Rodriguez, F. A., & de la Novalpons, M. B. (2015). Response of 
maize (zea mays l.) crop to biofertilization with plant growth promoting rhizobacteria and 
chitosan under field conditions. Journal of Experimental Biology and Agricultural Sciences: 
DOI: http://dx.doi.org/10.18006.3 (6).566.574 
Baghizadeh, A., Baniasadi, F., Bonjar, G.H.S., Sirchi, G.R.S., Massumi, H., Jorjandi, M., 
Farokhi, P.R. & Aghighi, S. (2009). Biocontrol of B otrytis allii Munn the causal agent of 
neck rot, the post-harvest disease in onion, by use of a new Iranian isolate of Streptomyces. 
Am. J. Agric. Biol. Sci., 4: 72- 78. 
Baliyan, S.P. (2014). Evaluation of Onion Varieties for Productivity Performance in Botswana. 
World Journal of Agricultural Research, vol. 2, no. 3: 129-135. Doi: 10.12691/wjar-2-3-8. 
Baliyan, S.P. and Kghati, D.L. (2009). Production and marketing problems in small scale 
horticultural farming in Botswana. Proceeding of the XVI International Symposium on 
Horticultural Economics and Management. Acta Hort. (ISHS) 831: 31-40.  
Baize, D. (2000). Guide des analyses en pédologie, 2ème édition revue et augmentée. INRA, Paris. 
Benkeblia, N., Varoquaux, P., Shiomi, N. & Sakai, H. (2002). Storage technology of onion 
bulbs cv. Rouge Amposta: effects of irradiation, maleic hydrazide and carbamate isopropyl, 
N-phenyl (CIP) on respiration rate and carbohydrates. Int. J. Food Sci. Tech. 37, 169-175. 
Best, K. (2000). Red Onion Cultivars Trial. Horticultural Nova Scotia, Kentville Agricultural 
Centre, Nova Scotia, Canada. pp. 10-13.  
Bettson, D. J. (1961). The production and marketing of onions in the Bawku area. Ghana Ministry 
of Agriculture Publication. (Mimeograph.) 
91 
 
University of Ghana http://ugspace.ug.edu.gh
Bhatt, V. K., Patel, P. T., & Bhatt, R. K. (2007). Effect of methods and dates of sowing on yield 
of green onion in Kharif under North Gujarat conditions. Ind. J. Hort., 64(4): 475-476. 
Biswas, S.K., Khair, A., Sarker, P.K., & Alom, M.S. (2010). Yield and storability of onion 
(Allium cepa L.) as affected by varying levels of irrigation. Bangladesh Journal of 
Agricultural Research 35(2):247-255. 
Black, C.A. (1965). Methods of Soil Analysis, 9 (Ed). American Society of Agronomy, Madison, 
pp. 545-567. 
Blay, E. T., Danquah, E. Y., Ofosu-Anim, J. & Ntumy, J. K. (2002). Effects of poultry manure 
and/or inorganic fertilizer on the yield of shallot (Allium cepa var. aggregatum). Advance 
Horticulture Science. 16(1): 13 – 16. 
Blay, E.T., Danquah, E.Y., Ofosu-Anim, J., & Ntumy, J.K. (2006). Effects of poultry manure 
and/or inorganic fertilizer on the yield of shallot (Allium cepa var. aggregatum). Adv. Hortic. Sci., 
vol 16,   no. 1, pp. 7-128. 
Bok, I., Madisa, M., Machacha, M., Moamogwe, M. & More, K. (2003). Manual for vegetable 
production in Botswana. Department of Agricultural Research, Gaborone, Botswana. 
Bosch Serra, A.D. & Currah, L. (2002). Agronomy of onions. In: H.D. Rabinowitch & L. Currah 
(eds.). Allium crop science: recent advances. CAB International, Wallingford, United 
Kingdom. 
Bosekeng, G. (2012). Response of onion (Allium cepa L.) to sowing date and plant population. 
Thesis, Department of Soil, Crop and Climate Sciences, Faculty of Natural and Agricultural 
Sciences, University of the Free State, pp. 156 
92 
 
University of Ghana http://ugspace.ug.edu.gh
Boukary, H., Haougui, A., Barage, M., Adam, T., Roumba, A., & Saadou, M. (2012a). 
Evaluation agro-morphologique des varietes et/ou ecotypes locaux d’oignon du Niger. Int J 
Biol Chem Sci 6(6):3098-3106. 
Boukary, H., Roumba, A., Adam, T., Barage, M. & Saadou, M. (2012 b). Interactions entre la 
variabilite des ecotypes de l’oignon (Allium cepa L.) et les facteurs agro-climatiques au 
Niger. Tropicultura 30(4):209-215. 
Boyette, M.D., Sanders, D.C. & Estes, E.A. (2008). Maintaining the quality of North Carolina 
Fresh Produce. North Carolina Cooperative. Extension Service. North Carolina State Univ., 
USA.  
Boyhan, G. & Kelley, W.T. (2008). Variety selection and characteristics. In: G.E. Boyhan & 
W.T. Kelley (eds.). Onion production guide. Cooperative Extension. The University of 
Georgia, Georgia, United States of America.  
Bray, R.H. & Kurtz, L.T. (1945). Determination of total, organic, and available forms of 
phosphorus in soils. Soil Science, 59: 39-45. 
Brewster, J.L. (1990). The influence of cultural and environmental factors on the time of maturity 
of bulb onion crops. Acta Hort. 267, 289-296. 
Brewster, J.L. (1994). Onions and other vegetable Alliums (1st ed.). Wallingford, UK: CAB 
International. Pp. 3-16. ISBN 0-85198-753-2. 
Brewster, J.L. (2008). Onions and other Vegetable Alliums. (2nd ed.), CAB International, North 
America. 
Brice, J. L., Currah, A. M., Mulins, A. & Bancroft, R. (1997). Onion storage in the tropics: A 
practical guide to methods of storage and their selection. Chatham, U.K: Natural Resources 
Institute. 111 pp.  
93 
 
University of Ghana http://ugspace.ug.edu.gh
Brummell, D.A. (2006). Cell wall disassembly in ripening fruit. Functional Plant Biol. 33:103-
119. 
Brummell, D.A. & Harpster, M.H. (2004). Cell wall metabolism in fruit softening and quality 
and its manipulation in transgenic plants. Plant Mol. Biol. 47:311-340. 
Bystrická, J., Musilová, J., Vollmannová, A., Timoracká, M., Kavalcová, P. (2013). Bioactive 
components of onion (Allium cepa L): a review. Acta Aliment. 42(1), 11-22. 
Carpita, N.C., & Gilbeaut, D.M. (1993). Structural models of primary cell walls in flowering 
plants: consistency of molecular structure with the physical properties of the walls during 
growth. Plant J. 3:1-30. 
Chope, G.A., Terry, L.A. & White, P.J. (2006). Effect of controlled atmosphere storage on 
abscisic acid concentration and other biochemical attributes of onion bulbs. Postharv. Biol. 
Technol. 39, 233-242. 
Chung, B. (1989). Irrigation and bulb onion quality. Acta Hort. 247, 233-237. 
Comrie, A.G. (1997). Climatic and soil requirements for onions. Onions B.1, Agricultural 
Research Council, Vegetable and Ornamental Plant Institute, Pretoria, South Africa. 
Coolong, T.W. & 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. 
Coolong, T. W. (2007). Physiological factors affecting onion (Allium cepa L.) storability-cultural 
methods for improving postharvest quality. A Dissertation Submitted to the Graduate Faculty of 
The University of Georgia in Partial Fulfillment of the Requirements for the Degree of Doctor of 
Philosophy. p. 181 
94 
 
University of Ghana http://ugspace.ug.edu.gh
Coolong, T.W., Randle, W.M. & Wicker, L. (2008). Structural and chemical differences in the 
cell wall regions in relation to scale firmness of three onion (Allium cepa L.) selections at 
harvest and during storage. J. Sci. Food Agric. 88, 1277-1286. 
Craig, W. (2010). Vegetarianism and Vegetarian Nutrition, Andrews University, MI, USA. 
http//www. Vegetarian-nutrition. Info/updates/onions. (Accessed 03/12/11).  
Cramer, C.S. (2003). Performance of fall-sown onion cultivars using four seeding dates. J. Amer. 
Soc. Hort. Sci. 128, 472-478. 
Currah, L. & Proctor, F.G. (1990). Onion in tropical regions. Bulletin 35. Natural Ressources 
Institute, NRI, UK, p 2321. 
Dapaah, H.K., Judith, G.A., Kwabena, D. & Eliezer, B.B. (2014). Influence of Poultry Manure 
and NPK Fertilization on Growth, Yield and Storability of Onion (Allium cepa L.) Grown 
Under Rain-fed Conditions. American Journal of Experimental Agriculture 4(8): 866-878 
Daryl, D.B. (2004). Soil test interpretations and recommendations handbook. Originally written 
1983, pp.39 
Dawling, P., Schonbeck, M. & Maloney, C. (2006). Onions: Organic Production in Virginia. 
Virginia Association for Biological Farming Information Sheet. 6(6): 1 – 7. 
Day, P.R. (1965). Particle fractionation and particle size analysis. In: Black C.A. (Ed.), Methods 
of Soil Analysis. American Society of Agronomy, Madison, pp. 545-567. 
Dowuona, G.N.N., Atwere, P., Dubbin, W., Nude, P. M., Mutala, B. E., Nartey, E. K. & Heck, 
R. J. (2012). Characteristics of termite mounds and associated Acrisols in the coastal 
savannah zone of Ghana and impact on hydraulic conductivity. Natural Science. 4:423-437.  
95 
 
University of Ghana http://ugspace.ug.edu.gh
Dwivedi, Y.C., Kushwah, S.S. & Sengupta, S.K. (2012). Evaluation of onion varieties for 
growth, yield and quality traits under agroclimatic conditions of kymore plateau region of 
Madhya Pradesh, India. Agricultural Science Digest 32(4):326-328. 
Editors of Encyclopaedia Britannica. https:// www. Britannica.com/ editor/ the-editors-of- 
encyclopaedia-britannica/4419 
Eksteen, G.J., Van Den Klashorst, E. & Van Ziji, B. (1997). Onions for export harvesting, 
handling and storage. Onions J.2. Agricultural Research Council, Vegetable and 
Ornamental Plant Institute, Pretoria, South Africa. 
EL-Tantawy, E.M. & EL-Beik, K.A. (2009). Relationship between growth, yield and storability 
of onion (Allium cepa L.) with fertilization of nitrogen, sulphur and copper under calcareous 
soil conditions. Res. J. Agric. Biol. Sci. 5, 361-371. 
Eze, P. N. (2008). Characterization, classification and Pedogenesis of soils on a Legon catena in 
the Accra plains, Ghana. Unpublished MPhil Thesis. University of Ghana, Legon, Accra, 
pp. 126. 
FAO (2000). Production Yearbook Vol. 54. Food and Agriculture Organization of the United 
Nations, Rome, Italy, 152 pp.  
FAO (2005). UN Food and Agriculture Organization (Onions).  
http//www.answers.com/topic/onion._note 25 (Accessed 1/11/10). 
FAO (2009) (United Nations, Food and Agriculture Organization), FAOStat (02/2001). World 
dry-bulb onion yield per hectare, 1990-2009.  
http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID=567#ancor 
FAOSTAT (2004). Food and agricultural commodities production. Food and Agricultural 
organization Statistics. http://faostat.fao.org/site/339/default.aspx 
96 
 
University of Ghana http://ugspace.ug.edu.gh
FDA (Food and Drug Administration) (2018), which regulates food labeling through the 
National Labeling and Education Act. 
Fern, Ken; Fern, Addy (2013). "Allium cepa L.". Plants for a Future. Retrieved 2013-03-22. 
Fuseini, A. (2012). Influence of NPK fertilizer application and bulb size at planting on growth and 
yield of onion. B.Sc. Thesis, University for Development Studies, Tamale. 
Galvan, G., Gonzalez Idiarte, H. & Sollier, S. (1997). Productive adaptation of onion (Allium 
cepa L.) landraces used for postharvest storage. Acta Hort. 433, 165-170. 
Garcia, E., M. Alviar-Agnew, and D.M. Barrett. (2002). Residual pectinesterase activity in 
dehydrated onion and garlic products. J. Food Processing Preservation. 26:11-26. 
Gautam, I.P., Khatri, B. & 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. 
Gemma, A.C.; L.A. Terry & P.J. White (2007). Effect of controlled atmosphere storage on 
abscisic acid concentration and other biochemical attribute of onion bulbs. Post-harvest 
Biology and Tech., 39: 233-242. 
Getahun, D., Zelleke, A., Deros, E. & Kiflu, E. (2003). Storability of shallot cultivars (Allium 
cepa L. var. ascalonicum Baker) at Debre Zeit, Ethiopia. Acta Hort. 604, 639-646. 
Ghana-Made (2017). Onions production in Ghana. Ghana-made.org (Accessed 30/05/17, 4:49 
pm). 
GhanaVeg (2018). GhanaVeg begins trials of eight onion varieties, p.34. 
Ghanaweb (2012). Onion_Farmers_Demand-Assitance. Available at  
www.ghanaweb.com/GhanaHomePage/newsArchive /Onion_Farmers_Demand-Assitance- 
257063. Accessed on 22nd January 2016  
97 
 
University of Ghana http://ugspace.ug.edu.gh
Gomez-Galindo, F., W. Herppich, V. Gekas, and I. Sjoholm. (2004). Factors affecting quality 
and postharvest properties of vegetables: Integration of water relations and metabolism. 
Critical Rev. Food Sci. Nutr. 44:139-154. 
González, M.I. (1997). Effect of sowing date on the production of three storage varieties of onion 
in the eight regions of Chile. Acta Hort. 433, 549-554. 
Gormaz, J.G., Quintremil, S., Rodrigo, R. (2015). Cardiovascular disease: a target for the 
pharmacological effects of quercetin. Curr. Top. Med. Chem. 15 (17), 1735-1742. 
Grant, D.G. & Carter, B.V. (1994). The influence of cultural factors on the bulb of the onion 
(Allium cepa L.) cultivar ‘Pukekohe Longkeeper’. Acta Hort. 433, 527-532. 
Grant, D.G. & Carter, B.V. (1997). The influence of cultural factors on the bulb shape of the 
onion (Allium cepa L.) cultivar ‘Pukekohe Longkeeper’. Acta Hort. 433, 527-532. 
Grauert, P. (2014). Concepa: Important changes of onion plant behaviours on its way from seed 
to maturity; Peter Grauert; Norseco; Canada; August 2014, 64 slices. 
Gubb, I.R., & MacTavish, H.S. (2002). Onion Pre- and Postharvest Considerations. In H. D. 
Rabinowitch and L. Currah (eds.). Allium crop sciences: Recent advances. CAB 
International, Wallingford, UK. p. 233-266. 
Hamma, I.L. (2013). Growth and yield of onion as influenced by planting dates and mulching 
types in Samaru, Zaria. International Journal of Advance Agricultural Research. Samara 
College of Agriculture/ DAC/ABU, P.M.B. 1058 Samaru, Zaria, Nigeria. pp. 22-26. 
Hasegawa, A., Yabuki, H., Nabeura, T., Fukui, H. & Iwata, T. (2001). Evaluation of bulb shape 
and fresh-weight of different onion cultivars. Tech. Bull. Agric. Kagawa Univ. 53, 71-77. 
98 
 
University of Ghana http://ugspace.ug.edu.gh
Hasegawa, A., Kanechika, R., & Oguni, S. (2005). Effect of low temperature and chitosan on 
dormancy breaking and growth of young corms of three Arisaema species. Acta 
Horticultural 673: 603-609. doi: http://dx.doi.org/10.17660/ActaHortic.2005.673.83. 
Hassan, M.S., & Ayoub, A.T. (1978). Effect of N, P and K on onion in the Sudan, Gezira. 
Experimental Agriculture 14: 29-32. 
HCDA (2008). A report on domestic horticulture marketing and market infrastructure in Kenya. 
Horticultural Crops Development Authority, Nairobi, Kenya, pp: 63. http://www.hcda.or.ke 
Horneck, D.A., Sullivan, D.M., Owen, J.S. & Hart, J.M. (2011). Soil Test Interpretation Guide. 
EC 1478. p.12 
Hurst, W.C., Shewfelt, R.L. & Schuler, G.A. (1985). Shelf life and quality changes in summer 
storage onions (Allium cepa L.). J. Food Sci. 50, 761-763. 
Hygrotech (2009a). Onion variety profiles: Short day length. Hygrotech Sustainable Solutions. 
www.hygrotech.com (Accessed 10/05/09). 
Hygrotech (2009b). Onion variety profiles: Intermediate day length. Hygrotech Sustainable 
Solutions. www.hygrotech.com (Accessed 10/05/09). 
Iannotti, M. (2008). How to grow onions in the home garden.  
http://gardening.about.com/od/vegetables/a/Growing Onions.htm 
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., & Naiken M.V. (2008). Yield performance of four onions 
(Allium cepa L.) varieties compared with the local variety under open field conditions at 
Anse Boileau, Seychelles. Journal of Science and Technology 28(3):28-33. 
99 
 
University of Ghana http://ugspace.ug.edu.gh
Islam M.K., Alam M.F. & 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. 
Jarzabkowski, V. (2017). A nutritionist with the Fitness Institute of Texas at the University of 
Texas at Austin 
Javadzadeh, A., Ghorbanihaghjo, A., Bonyadi, S., Rashidi, M. R., Mesgari, M., 
Rashtchizadeh, N. & Argani, H. (2009). Preventive effect of onion juice on selenite-
induced experimental cataract. Ind. J. Ophthalmol., 57: 185-189. 
Jessie, S. (2017). A writer for Live Science. In the Jewish Daily Forward, National Geographic 
Traveler — Intelligent Travel, Killing the Buddha, Waccamaw Journal and elsewhere, at 
George Mason University. 
Jilani, M.S. & Ghafoor, A. (2003). Screening of Local Onion Varieties for Bulb Formation. 
International Journal of Agriculture and Biology, 5 (2), 129-133.  
Jones, H.A. & Mann, L.K. (1963). Onions and other allies. Inter science Publishers, Inc. New 
York, United States of America. 
Joubert, T.G. LA G. (1997). Harvesting, handling and storage of onions. Onions I.1. Agricultural 
Research Council, Vegetable and Ornamental Plant Institute, Pretoria, South Africa. 
Kabura, B.H., Musa, B., & Odo, P.E. (2008). Evaluation of the yield components and yield of 
onion (Allium cepa L.) and pepper intercrop in Sudan savanna. Journal of Agronomy 
7(1):88-92. 
Kandil, A.A., Leilah, A.A., Mostafa, A.K. & Fathalla, F.H. (2010). Study on the internal bulb 
quality of some new Egyptian onion cultivars under different irrigation regimes. J. of Plant 
Production, Mansoura Univ., 1 (2): 205-212. 
100 
 
University of Ghana http://ugspace.ug.edu.gh
Khokar, K.M., Mahmood, T. & Laghari, M.H. (2002). Effect of Planting Dates on Bulb Yield. 
Vegetable Crops Journal 4:3-5. 
Khokhar, K.M., Hadley, P. & Pearson, S. (2007). Effect of cold temperature durations of onion 
sets in store on the incidence of bolting, bulbing and seed yield. Sci. Hortic. 112, 16-22. 
Kimani, P.M., Kariuki, J.W., Peters, R. & Rabinowitch, H.D. (1993). Influence of the 
environment on the performance of some onion cultivars in Kenya. Afr. Crop Sci. J. 1, 15-
23. 
Komochi, S. (1990). Bulb dormancy and storage physiology, In: H.D. Rabinowitch and J.L. 
Brewster (eds.). Vol. 1. Onions and allied crops. CRC Press, Boca Raton, Fla. p. 89-111 
Kuete, V. (2017). Medicinal Spices and Vegetables from Africa. Therapeutic Potential against 
Metabolic, Inflammatory, Infectious and Systemic Diseases. Allium cepa L. University of 
Dschang, Cameroon. Available from: http://dx.doi.org/10.1016/B978-0-12-809286-
6.00014-5, pp. 353-361, (Chapter 14). 
Kyofa-Boamah, M., Blay, E., Braum, M. & Kuehn, A. (2000). Good Agricultural Practices and 
Crop Protection Recommendations for Selected Vegetables. Handbook of Crop Protection 
in Ghana 5: 95-108. 
Lacy, M.L. & Roberts, D.L. (1982). Yield of Onion Cultivars in Midwestern Organic Soils 
Infested With Fusarium oxysporium f. sp. cepae and Pyrenochaeta terrestris. Plant Disease  
66:1003-1006. 
Lancaster, J.E., Farrant, J. & Shaw, M.L. (2001a). Sulfur nutrition affects cellular sulfur, dry    
weight distribution, and bulb quality in onion. J. Amer. Soc. Hort. Sci. 126, 164-168. 
Lancaster, J.E., Farrant, J., Shaw, M., Bycroft, B. & Brash, D. (2001b). Does sulphur supply 
to the bulb affect storage of onions? Acta Hort. 555, 111-115. 
101 
 
University of Ghana http://ugspace.ug.edu.gh
Lancaster, J.E., Triggs, C.M., De Ruiter, J.M. & Gandar, P.W. (1996). Bulbing in onions: 
photoperiod and temperature requirements and prediction of bulb size and maturity. Ann. 
Bot. 78, 423-430. 
Larsen, T., Saxena, A. & Cramer, C.S. (2009). Relatedness of bulb firmness to other attributes 
of New Mexico onion entries. Int. J. Veg. Sci. 15, 206-217. 
Lawande, K.E. (2012). Onion. In: Peter, K.V. (Ed), Handbook of Herbs and Spices; second ed. 
Woodhead Publishing, pp. 417-429, (Chapter 23). 
Mahanthesh, B., Ravi Prasad Sajjan, M., Harshavardhan, M.,  & Vishnuvardhana 
Janardhan, G. (2008). Evaluation of different onion (Allium cepa L.) genotypes for yield 
and processing quality parameters in Kharif season under irrigated condition. The Asian 
Journal of Horticulture 3(1):5-9. 
Mallor, C., Balcells, M., Mallor, F. & Sales, E. (2011). Genetic variation for bulb size, soluble 
solids content and pungency in the Spanish sweet onion variety Fuentes de Ebro. Response 
to selection for low pungency. Plant Breed. 103, 55-59. 
Mettananda, K.A. & Fordham, R. (1999). The 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. Biotechnol. 
74, 622-631. 
Micheli, F. (2001). Pectin methylesterases: cell wall enzymes with important roles in plant 
physiology. Trends in Plant Sci. 6:414-419. 
Mishu, H.M., Ahmed, F, Rafii, M.Y., Golam, F. & Latif, M.A. (2013). Effect of sulphur on 
growth, yield and yield attributes in onion (Allium cepa L.). AJCS 7(9):1416-1422. 
102 
 
University of Ghana http://ugspace.ug.edu.gh
Mitiku, M. & Tadesse, A. (2017). “Adaptability Study of Improved onion (Allium cepa L.) 
Varieties at South Ari Woreda of South Omo Zone, Ethiopia.” International Journal of 
Research - Granthaalayah, 5(7), 541-545. doi.10.5281/zenodo.839814. 
MoFA (Ministry of Food and Agriculture) (2013). Yearly production figures and beneficiary 
by crop of dry season. Annual Report MoFA; Republic of Ghana. 
Mohammadi-Fatideh, M. & Hassanpour-Asil, M. (2012). Onion yield, quality and storability 
as affected with different soil moisture and nitrogen regimes. South Western Journal of 
Horticulture, Biology and Environment. 3(2): 145 – 165. 
Mohanty, B.K. & Prusti, A.M. (2001). Performance of common onion varieties in Kharif 
seasons. Journal of Tropical Agriculture 39:21-23.  
Mondal, M.F., Brewster, J.L., Morris, G.E.L. & Butler, H.A. (1986c). 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. 
Moulin, M.M., Rodrigues, R., Goncalves, L.S.A, Sudre, C.P., dos Santos, M.H. & da Silva, 
J.R.P. (2012). Collection and morphological characterization of sweet potato landraces in 
North of Rio de Janeiro state. Hortic Bras 30(2):286-292. 
Msuya, D.G., Reuben, S.O.W.M., Mbilinyi, L.B., Maerere, A.P., Msogoya, T., Mulungu, L.S. 
& Misangu, R.N. (2005). Evaluation of field performance and storage of some tropical 
short-day onion (Allium cepa L.) cultivars. W. Afr. J. Ecol. 8,10-18. 
Nagaraju, R., Haripriva, K., Rajalingam, G.V., Sriamachandrasekarn, V. & Mohideen, 
M.K. (2000). Effect of VAM on growth and yield of aggregatum onion (Allium cepa L. var. 
aggregatum Don). South Indian Hortic, 48: 40-45. 
103 
 
University of Ghana http://ugspace.ug.edu.gh
Narla, R.D., Muthomi, J.W., Galchu, S.M., Nderitu, J.H. & Olubayo, F.M. (2011). Effect of 
intercropping Bulb Onion and Vegetables on Purple Blotch and Downy Mildew. Journal of 
Biological Sciences, 11: 52-57.  
NARSP (National Agricultural Strategic Research Plan) Ghana (1994). Final Report. 
Nasreen, S., Haque, M.M., Hossain, M.A., & Farid, A.T.M. (2007). Nutrient uptake and yield 
of onion as influenced by nitrogen and sulphur fertilization. Bangladesh J Agri Res 
32(3):413-420. 
Nasreen, S., Imamul, H.A.Q.S.M.  & Hossain, M.A. (2003). Sulphur effects on growth 
responses and yield of onion. Asian J. Plant Sci. 2, 897-903. 
NAD (National Agricultural Directory) (2009). Field crops and horticulture. Vegetables. 
Department of Agriculture, Pretoria, South Africa. 
Necola, S. (2007). Allium cepa Variety Evaluation for Organic Farming in the 5th International 
Symposium on Edible Allianceae. Dronten The Netherlands. ISHS. 45pp. 
Nigussie, A., Yitagesu, K., Abiy, A., Tigist, A., & Kidane, D. (2015). Onion Production for 
Income Generation in Small Scale Irrigation Users Agropastoral Households of Ethiopia. 
Journal of Horticulture: doi.org/10.4172/2376-0354.1000145 
Nilufar, Y. (2009). Morphological characterization and genetic diversity of onion (Allium cepa 
L.). Master’s Thesis, Faculty of Agriculture, Sher-E-Bangla Agricultural University, Dhaka, 
71pp. 
NOA (National Onion Association) (2011). How and where onions are grown. 
https://www.onions-usa.org/all-about-onions/ where-how -onions-are-grown. 
Norman, J. C. (1992). Tropical Vegetable Crops Arthur H. Stockwell Ltd. Devon, UK. 234pp. 
104 
 
University of Ghana http://ugspace.ug.edu.gh
O’Donoghue, E.M., Somerfield, S.D., Shaw, M., Bendall, M., Hedderly, D., Eason, J., & Sims, 
I. (2004). Evaluation of Carbohydrates in Pukekohe Longkeeper and Grano cultivars of 
Allium cepa. J. Agri. Food Chem. 52:5383-5390. 
Obeng-Ofori, D., Danquar, E.Y. & Ofosu-Anim, J. (2007). Vegetable and Spice Crop 
Production in West Africa, The City Publishers Limited, Ghana. Pp 77-79. 
Okporie, E.O. & Ekpe, 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. 
Olsen, S.R., Cole, C.V., Watanabe, F.S. & Dean, L.A. (1954). Estimation of available 
phosphorus in soils by extraction with sodium bicarbonate. USDA Circular 939. U.S. 
Government Printing Office, Washington D.C.  
Pavlovic, N., Zecevic, B., Zdravkovic, M., Ivanovic, M., & Damjanovic, M. (2003). Variability 
and heritability of average yield of onion bulb (Allium cepa L.). Genetika 35(3):149-154. 
Peretto, R., Favaron, F., Bettini, V., Delorenzo, G., Marini, S., Alghisi, P., Cervone, F. & 
Bonfante, P. (1992). Expression and localization of polygalacturonase during the 
outgrowth of lateral roots in Allium porrum L. Planta, 188:164-172. 
Perez, A.P., Decon, L.M. & Mayer, Z.F. (1996). Influence of onion bulb size and its locality of        
origin on seed yield. Onion Newslett. Trop., 7: 25-32. 
Peters, R.J., Kowithayakorn, T., Chalard, T. & 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. 
POVD (Protocol for Onion variety demonstration) (2016). Evaluation of different onion 
varieties on potential yield and agronomic performance in Uganda (ZARDI Mukono). p.11 
PROKON (2016). Onion Training Manual. p. 78 
105 
 
University of Ghana http://ugspace.ug.edu.gh
Quadir, M.A. & Boulton, A. (2005). Yield and maturity of new released red onion cultivars in 
New South Wales. Acta Hort. 694, 117-119. 
Rahman, M. & Das, M.K. (1985). Simple correlation coefficient and path coefficient analysis in 
garlic (Allium sativum L.). Bangladesh J. Agril. Res. 10 (1): 50-54. 
Rahn, C.R., Shepherd, M.A. & Hiron, R.W.P. (1996). The effect of water supply on the 
response of onions and calabrese to starter solutions. Acta Hortic. 428: 141-150. 
Raju, K. & Naik, M. K. (2007). Survey and assessment for the post-harvest diseases of onion in 
North-Eastern Karnataka. Karnataka Journal of Agriculture Science, 20(1): 164-165. 
Ramin, A.A. (1999). Storage potential of bulb onions (Allium cepa L.) under high temperatures. 
J. Hort. Sci. Biotechnol. 74, 181-186. 
Reddy, K.C., & Reddy, K.M. (2005). Different levels of vermin compost and nitrogen on growth 
and yield in onion (Allium cepa L.) – raddish (Raphanus sativus L.) cropping system. J. Res. 
ANGRAU; 33(1):11-17. 
Rivera-Martinez, A., Fernandez Paz, J., & Andres Ares, J.L. (2005). Evaluation of local onion 
lines from northwest Spain. Spanish Journal of Agricultural Research 3(1):90-97. 
Rizk, F.A. (1997). Productivity of onion plant (Alliun cepa L.) as affected by method of planting 
and NPK application. Egyptian J. Hort; 24(2):219-238. 
Ro, J.Y., Ryu, J.H., Park, H.J. & Cho, H.J. (2015). Onion (Allium cepa L) peel extract has anti-
platelet effects in rat platelets. Springerplus 4, 17. 
Rouamba, G.R.H., Ba, D., Ricroch, A. & Currah, L. (2001). Agronomic and physiological 
evaluation of some regional populations of onion in field and storage trials in West Africa  
SAKATA (2014). Technical Bulletin Ref. Red Creole. Website. www.sakata.com 
106 
 
University of Ghana http://ugspace.ug.edu.gh
Shaikh, A.M., Vyakaranahal, B.S., Shekhargouda, M., & Dharmatti, P.R. (2002). Influence 
of bulb size and growth regulators on growth, seed yield and quality of onion cv Nasik Red. 
Seed Sci. Res vol. 30, pp. 223-229. 
Silue, S., Fondjio, L., Coulibaly, M.Y., & Magein, H. (2003). Selection of onion varieties 
(Allium cepa L.) adapted to Cote d’Ivoire. Tropicultura 21(3):129-134. 
Sinclair, P. (1989). Physiology of the onion. Aus. Onion Grower 6, 7-9. 
Singh, T., Singh, S.B., & Singh, B.N. (1989). Effect of nitrogen, potassium and green manuring 
on growth and yield of rainy season onion (Allium cepa L.). Narendra Deva J. Agric. Res. 
4 (1):57-60. 
Sinnadurai, S. (1973). Shallot farming in Ghana. Econ. Bot. 27:438-441. 
Sinnadurai, S. & Abu, J. F. (1977). Onion Farming in Ghana. Economic Botany, Vol. 31, No. 3 
(Jul. - Sep., 1977), pp. 312-314 
Sinnadurai, S. (1992). Vegetable cultivation. Asempa Publishers, Accra, Ghana Pages: 83. 
Smith, C. (2003). Genetic Analysis of Quercetin in Onion (Allium cepa L.) ‘Laddy Raider. The 
Texas Journal of Agriculture and Natural Resource, 16, 24-28.  
Smith, C.J.S., Watson, C.F., Morris, P.C., Bird, C.R., Seymour, G.B., Gray, J.E., Arnold, C., 
Tucker, G.A., Schuch, W., Harding, S., & Grierson, D. (1990). Inheritance and effect on 
ripening of antisense polygalacuronase genes in transgenic tomatoes. Plant Mol. Biol. 
14:369-379. 
Soil Science Laboratory, University of Ghana, Legon (2018). Physico-chemical properties of 
the experimental sites analysis. 
SSS (Soil Survey Staff) (1998). Keys to soil Taxonomy, Soil Conservation service, United States 
Department of Agriculture. Blacksburg Virginia. USA, Pocahontas Press Inc., pp. 599. 
107 
 
University of Ghana http://ugspace.ug.edu.gh
Soleymani, A. & Shahrajabian, M. H. (2012). Effects of different levels of nitrogen on yield and 
nitrate content of four spring onion genotypes. Inter. J. of Agric. and Crop Sci., 4(4): 179-
182. 
STARKE AYRES (2014). Onion Production Guideline-final. Pdf, 4p. 
Sultana, S., Paul, A. K., Sultana, D. & Sarker, J. R. (2014). Influence of integrated organic-
inorganic nitrogen on growth and nutrient concentration of summer onion (Allium cepa L.) 
Bangladesh Journal Agricultural Research. 39(3): 529 – 545. 
Suslov, D., Verbelen, J. P. & Vissenberg, K. (2009). "Onion epidermis as a new model to study 
the control of growth anisotropy in higher plants". Journal of Experimental Botany 60 (14): 
4175–87. doi:10.1093/jxb/erp251. PMID 19684107. 
Suthamathy, N. & Seran, T.H. (2011). Growth and yield response of red onion (Allium 
ascalonicum L.) grown in different potting media. Journal of Phytology 3(1):50-58.  
Tarpaga, M.W.V., Albert, R. & Zoumbiesse, T. (2011). Effects of seasons of bulb seed 
production on the early bolting of onion (Allium cepa L.) cv. ‘Violet de Galmi’. J. Appl. 
Biosci. 40, 2652-2658. 
Tesfay, S.Z., Bertling, I., Odindo, A.O., Greenfield, P.L., & 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. 
Trias, N.G.O. (2010). Onions are a Source of Income in Ghana, Newsletter. 
www.Triasngo.org/onions (Accessed 27/03/2012). 
Trivedi, A.P. & Dhumal, K.N. (2010). Variability and correlation studies on bulb yield, 
morphological and storage characters in onion (Allium cepa L.). Journal of Pure and 
Applied Sciences, 18:1-4. Trop Sciences 41:78-84. 
108 
 
University of Ghana http://ugspace.ug.edu.gh
Tsitsia, R.K. (2012). Influence of cultivar and bulb size at planting on growth and yield of onion. 
B.Sc. Thesis, University for Development Studies, Tamale.  
Tweneboah, C.K. (2000). Vegetable and species in West Africa. Co-Wood Publishers, Accra, 
Ghana, pp: 148-152.  
UNEP (United Nations Environment Programme) (2002). Project Development Facility .Volta 
River Basin Preliminary Transboundary Diagnostic Analysis-Final Report. 
USPO (United States Patent Office) (2011): Method of coloring eggs or the like". 1925-06-19. 
Retrieved 2011-09-17.  
USAID (2009). Onion information sheet. Section 1 and 2: Production and marketing and TIPCEE 
intervention, p.4 
USAID-Inma (2012). Onion Production: Planting Through Harvest. http:// www.inma-iraq.com. 
pp.56. 
USDA (United States Salinity Laboratory Staff) (1969). Agriculture Handbook No.60: 
(Diagnosis and Improvement of Saline and Alkali Soils). 
Valenzuela, H., Shimabuku, R., Kratky, B. & Hamasaki, R. (1999). Onions in Hawaii and 
around the world. In: R. Hamasaki, H. Valenzuela & R. Shimabuka (eds.). Bulb production 
in Hawaii. College of Tropical Agriculture and Human Resources. Manoa, Hawaii. 
Volk, G.M. (2009). Phenotypic characteristics of ten garlic cultivars grown at different North 
American Locations. Hortscience 44(5):1238-1247. 
Weerasinghe, S.S. & Fordham, R. (1994). The effects of plant density on onions established 
from multiseeded transplants. Acta Hort. 371, 97-104. 
White, R.M. (1969). Measurement of soil pH. Journal of Australian Institute of Agriculture 
Science. 35: 3-14. 
109 
 
University of Ghana http://ugspace.ug.edu.gh
Wickramasinghe, U.L., Wright, C.J. & 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. 
Wiedenfeld, R. (1994). Nitrogen rate and timing effects on onion growth and nutrient uptake in a 
subtropical climate. Subtrop. Plant Sci., 46: 32-37. 
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. 
Wiles, G.C. (2006). On-station vegetable variety trials report. Department of Agricultural 
Research, Ministry of Agriculture, Government of Botswana, Gaborone, Botswana.  
World Weather (2018). Meteorological data of the trial site at Sogakope and Legon. 
https://www.worldweatheronline.com (Accessed 24/04/18; 4:59 pm). 
Wright, P.J. & 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. 
Xu, K., Huang, X., Wu, M., Wang, Y., Chang, Y., Liu, K., Zhang, J., Zhang, Y., Zhang, F., 
Yi, L., Li, T., Wang, R., Tan, G. & Li, C. (2014). "A rapid, highly efficient and economical 
method of Agrobacteriummediated in planta transient transformation in living onion 
epidermis". PLoS ONE 9 (1): e83556. doi:10.1371/journal.pone.0083556. PMC 3885512. 
PMID 24416168. 
Yadav, R.L., Sen, N.L. & Yadav, B.L. (2003). Response of onion to nitrogen and potassium 
fertilization under semi-arid condition. Indian J. Hort.;60 (2):176-178. 
Yohannes, K.K., D. & Debela, A. (2013). Effect of farmyard manure and nitrogen fertilizer rates 
on growth, yield and yield components of onion (Allium cepa L.) at Jimma, Southwest 
Ethiopia. Asian Journal of Plant Sciences. 10: 1-7. 
110 
 
University of Ghana http://ugspace.ug.edu.gh
APPENDICES 
Appendix 1: Onion nutrition facts 
 
Onion Nutrition Facts Serving Size 1 Medium Onion (148 g) Percent Daily Values * 
Calories 64 3 % 
Total Carbohydrate 11 g 4 % 
Total Fat 0 0 % 
Cholesterol 0 0 % 
Dietary Fiber 3 g 12 % 
Sugars 9 g 0 % 
Protein 1.6 g 3 % 
Vitamins 
Vitamin A 3 IU 0 % 
Vitamin C 11.8 mg 20 % 
Vitamin B6 0.2 mg 9 % 
Folate 28.5 mcg 7 % 
Minerals 
Calcium 36.8 mg 4 % 
Iron 3 mg 2 % 
Magnesium 15 mg 4 % 
Phosphorus 43.5 mg 4 % 
Potassium 190 mg 5 % 
Sodium 6.4 0 % 
Zinc 3 mcg 2 % 
Copper 0.1 mg 3 % 
Manganese 0.2 mcg 10 % 
Selenium 0.7 mcg 1 % 
Fluoride 1.8 mcg 0 % 
Other 
Alcohol 0.0 g  
Water 143 g 
Ash 0.6 g 
Caffeine 0.0 mg 
*Percent (%) Daily Values are based on a 2,000 calorie diet. Your Daily Values may be higher or 
lower depending on your calorie needs. 
Source: Food and Drug Administration (FDA) 
  
111 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 2: Plant structure of a young onion plant in the vegetative growth stage 
 
 
 
 
 
Figure 2: Plant structure of a young onion plant in the vegetative growth stage (Brewster, 
1994) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
112 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 3: Different onion bulb shapes 
 
 
 
Figure 3: Different onion bulb shapes (1) Flattened (2) Globe (3) High globe (4) Spindle (5)            
Spanish (6) Flat (7) Thick flat (8) Granex (9) Top (Boyhan & Kelley, 2008) 
 
 
 
 
 
 
 
 
 
113 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 4: Field trial layout 
 
Figure 4: Field trial layout 
 
 
 
 
 
 
114 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 5: Plot layout 
 
Figure 5: Plot layout indicating number of plants and the harvested area 
 
115 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 6: Soil texture triangle 
 
 
Figure 6: Soil texture triangle 
Source: USDA textural triangle 
 
 
116 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 7: Soil test interpretation guide 
 
pH (Water)  
pH  Interpretation  
< 5.4 Strongly acidic  
Aluminium (Al) or Manganese (Mn) toxicity  
Can have Molybdenum deficiencies  
Ca, Mg, and K deficiency (Due to possible leaching)  
Reduced microbial activity  
5.5-6.4 Moderately acidic  
6.5-6.9 Slightly acidic  
7.0 Neutral  
7.1-7.5 Slightly Alkaline  
7.6-8.3 Moderately alkaline  
>8.4 Strongly alkaline  
pH (CaCl2)  
<4.8 Strongly acidic  
Possible Al and Mn Toxicity and Mo Deficiency  
4.8-5.2 Moderately high acidic  
Acceptable for acid tolerant species  
5.2-5.5 Moderately acidic  
5.5-7.5 Moderately acidic to slightly alkaline  
Above 6.5 - Often high in Mg and calcium carbonate  
>7.5 Moderately to strongly alkaline  
 
Source: Arris Pty Ltd. www.arris.com.au 
 
 
 
 
 
117 
 
University of Ghana http://ugspace.ug.edu.gh
Soluble salts determined from a saturated paste extract. 
 EC (mmhos/cm)* ppm salt† Suitability for crop production 
Low <1.0 <640 Suitable 
Medium 1.0-2.5 640-1,600 Marginal 
High >2.5 >1,600 Poor, unsuitable for many crops 
 
Note: Some laboratories determine EC using a 1:1 or 2:1 ratio of water to soil, which provides a 
substantially lower value than the saturated paste extract. No relationship has been established for 
converting 1:1 or 2:1 EC to saturated paste EC. 
* mmhos/cm is equivalent to deci-siemen/m (dS/m) and milli-siemen/cm (mS/cm). 
† Multiply mmhos/cm by 640 to estimate ppm salt. 
Source: Horneck et al. (2011) 
 
Nitrogen rate adjustments based upon soil texture and organic matter. 
Soil Texture Cation Exchange Capacity Organic Matter Soil N Credit 
 Meq/100g (%) Ibs.N/A 
Sand-  ≤ 0.5 20 
Sandy loam ≤ 10 0.6 to 1.4 OM x 40 
 ≥ 1.5 60 
Silt loam –  ≤ 2.0 40 
Loam 10-18 2.1 to 3.9 OM x 20 
≥ 4.0 80 
  ≤ 2.0 20 
Clay loam – ≥ 18 2.1 to 4.9 OM x 10 
Clay ≥ 5.0 50 
Source: Daryl (2004) 
 
 
 
118 
 
University of Ghana http://ugspace.ug.edu.gh
Total N (%) 
Rating (% by weight)  Description 
<0.05  Very low 
0.05 – 0.15  Low 
0.15 – 0.25  Medium 
0.25 – 0.50  High 
>0.5  Very High 
Source: Natural Resources South East. Brian Hughes, David Davenport and Lyn Dohle 
 
Phosphorus (P) soil test categories. 
 Bray test P Olsen test P 
(ppm) (ppm) 
Low <20 <10 
Medium 20-40 10-25 
High 40-100 25-50 
Excessive >100 >50 
Source: Horneck et al. (2011) 
 
Extractable potassium (K) soil test categories. 
 Extractable or soil test K 
Low <150 ppm* 
<0.4 meq/100 g soil 
Medium 150–250 ppm 
0.4–0.6 meq/100 g soil 
High 250–800 ppm 
0.6–2.0 meq/100 g soil 
Excessive >800 ppm 
>2.0 meq/100 g soil 
 
* For ammonium acetate or sodium bicarbonate extraction method. 
Source: Horneck et al. (2011) 
119 
 
University of Ghana http://ugspace.ug.edu.gh
Extractable magnesium (Mg) soil test categories. 
 Extractable or soil test Mg 
Low <60 ppm 
<0.5 meq/100 g soil 
Medium 60–300 ppm 
0.5–2.5 meq/100 g soil 
High >300 ppm 
>2.5 meq/100 g soil 
Source: Horneck et al. (2011) 
 
Sulfate-sulfur soil test categories. 
 Soil test sulfate-S (ppm) 
Very low <2 
Low 2-5 
Medium 5-20 
High  >20* 
* When sulfate-S soil test values are high, determine soil and irrigation water electrical 
conductivity. 
Source: Horneck et al. (2011) 
 
Extractable boron (B) soil test categories. 
 Soil test B (ppm) 
Very low <0.2 
Low 0.2–0.5 
Medium 0.5–1 
High 1–2 
Excessive >2† 
† When soil test B is excessive, determine soil and irrigation water electrical conductivity and B 
in irrigation water. 
Source: Horneck et al. (2011) 
 
120 
 
University of Ghana http://ugspace.ug.edu.gh
Ratings for DTPA extractable micronutrient soil test levels. 
Soil Test Rating Zinc Iron Manganese Copper 
Low 0-0.5 ppm 0-2.0 ppm 0-1.0 ppm 0-0.2 ppm 
Medium 0.5-1.0 ppm 2.1-4.5 ppm - - 
High 1.0 + 4.6 + 1.0 + 0.2 + 
Source: Daryl (2004) 
 
 
Base saturation 
Base saturation is the percentage of the soil CEC that is occupied by basic cations (calcium, 
magnesium, potassium, sodium) at the current soil pH value. Base saturation and CEC are nearly 
equivalent (base saturation is 100 percent) when soil pH is near 7. An acidic soil has a base 
saturation of about 50 percent when the soil pH is about 5. Since base saturation is simply an 
indirect expression of soil pH, it is not required for making fertilizer or lime recommendations. In 
acidic soils, base saturation and soil pH change simultaneously. Liming increases base saturation 
and soil pH. Sulfur application will reduce base saturation and pH. Base saturation is not a useful 
concept in alkaline soils, where base saturation equals or exceeds 100 percent Horneck et al. 
(2011). 
 
 
 
 
 
 
 
 
 
 
121 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 8: Analysis of variance for Sogakope experiment  
 
Variate: Crop establishment (%) at four week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0. 0.   
Treatments 4 0 0   
Residual 12 0 0   
Total  19 0    
 
Variate: Crop establishment (%) at six week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0. 0.   
Treatments 4 0 0   
Residual 12 0 0   
Total  19 0    
 
Variate: Crop establishment (%) at eight week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.07000 0.02333 035  
Treatments 4 0.75200 0.18800 2.82 0.073 
Residual 12 0.80000 0.06667   
Total  19 1.62200    
 
Variate: Number of leaves at four week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.4680 0.1560 0.97  
Treatments 4 9.3530 2.3383 14.56 < .001 
Residual 12 1.9270 0.1606   
Total  19 11.7480    
 
122 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Number of leaves at six week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 1.3560 0.4520 0.45  
Treatments 4 3.7080 0.9270 0.93 0.480 
Residual 12 11.9840 0.9987   
Total  19 17.0480    
 
Variate: Number of leaves at eight week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 3.220 1.073 0.45  
Treatments 4 25.663 6.416 2.70 0.082 
Residual 12 28.525 2.377   
Total  19 57.408    
 
Variate: Plant height at four week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 103.806 34.602 3.87  
Treatments 4 639.042 159.760 17.88 < .001 
Residual 12 107.242 8.937   
Total  19 850.090    
 
Variate: Plant height at six week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 33.324 11.108 1.86  
Treatments 4 981.325 245.331 41.01 < .001 
Residual 12 71.791 5.983   
Total  19 1086.440    
 
 
 
123 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Plant height at eight week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 5.67 1.89 0.04  
Treatments 4 1936.89 484.22 10.03 < .001 
Residual 12 579.24 48.27   
Total  19 2521.80    
 
Variate: Stem diameter at four week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 3.1224 1.0408 2.35  
Treatments 4 42.9102 10.7276 24.21 < .001 
Residual 12 5.3162 0.4430   
Total  19 51.3489    
 
Variate: Stem diameter at six week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 7.406 2.469 1.18  
Treatments 4 79.832 19.958 9.55 0.001 
Residual 12 25.085 2.090   
Total  19 112.323    
 
Variate: Stem diameter at eight week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 29.354 9.785 1.00  
Treatments 4 181.555 45.389 4.65 0.017 
Residual 12 117.249 9.771   
Total  19 328.158    
 
 
 
124 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Bulb sugar content at two weeks after harvesting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.946 0.315 0.12  
Treatments 4 22.112 5.528 2.13 0.139 
Residual 12 31.124 2.594   
Total  19 54.182    
 
Variate: Bulb sugar content at four weeks after harvesting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 2.524 0.841 0.68  
Treatments 4 18.272 4.568 3.70 0.035 
Residual 12 14.816 1.235   
Total  19 35.612    
 
Variate: Bulb firmness 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 27.605 9.202 1.52  
Treatments 4 67.013 16.753 2.76 0.077 
Residual 12 72.807 6.067   
Total  19 167.425    
 
Variate: Bulb length (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 152.36 50.79 1.27  
Treatments 4 216.55 54.14 1.36 0.306 
Residual 12 479.08 39.92   
Total  19 847.99    
 
 
 
125 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Bulb diameter (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 78.49 26.16 0.97  
Treatments 4 31.47 7.87 0.29 0.877 
Residual 12 322.88 26.91   
Total  19 432.83    
 
Variate: Average bulb weight (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 658.1 219.4 0.96  
Treatments 4 110.5 27.6 0.12 0.972 
Residual 12 2749.0 229.1   
Total  19 3517.7    
 
Variate: Rotten bulbs weight at four weeks after harvesting (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 206165 68722 7.15  
Treatments 4 38958 9740 1.01 0.439 
Residual 12 115339 9612   
Total  19 360463    
 
Variate: Healthy bulbs weight at four weeks after harvesting (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 271259 90420 5.58  
Treatments 4 77160 19290 1.19 0.364 
Residual 12 194402 16200   
Total  19 542820    
 
 
 
126 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Healthy bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 27.126 9.042 5.58  
Treatments 4 7.716 1.929 1.19 0.364 
Residual 12 19.440 1.620   
Total  19 54.282    
 
Variate: Rotten bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 20.6165 6.8722 7.15  
Treatments 4 3.8958 0.9740 1.01 0.439 
Residual 12 11.5339 0.9612   
Total  19 36.0463    
 
Variate: Total bulbs yield (kg/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 6.581E+08 2.194E+08 0.96  
Treatments 4 1.105E+08 2.763E+07 0.12 0.972 
Residual 12 2.749E+09 2.291E+08   
Total  19 3.518E+09    
 
Variate: Total bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 658.1 219.4 0.96  
Treatments 4 110.5 27.6 0.12 0.972 
Residual 12 2749.0 229.1   
Total  19 3517.7    
 
 
 
127 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 9: Analysis of variance for Legon experiment  
 
Variate: Seedling establishment (%) at four week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0. 0.   
Treatments 4 0 0   
Residual 12 0 0   
Total  19 0    
 
Variate: Seedling establishment (%) at six week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0. 0.   
Treatments 4 0 0   
Residual 12 0 0   
Total  19 0    
 
Variate: Seedling establishment (%) at eight week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.04000 0.01333 0.42  
Treatments 4 0.06800 0.01700 0.54 0.712 
Residual 12 0.38000 0.03167   
Total  19 0.48800    
 
Variate: Number of leaves at four week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.41350 0.13783 2.55  
Treatments 4 3.42300 0.85575 15.82 < .001 
Residual 12 0.64900 0.05408   
Total  19 4.48550    
 
128 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Number of leaves at six week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.1320 0.0440 0.29  
Treatments 4 1.1250 0.2813 1.87 0.180 
Residual 12 1.8030 0.1502   
Total  19 3.0600    
 
Variate: Number of leaves at eight week after transplanting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 1.1460 0.3820 1.10  
Treatments 4 15.0870 3.7717 10.91 < .001 
Residual 12 4.1490 0.3458   
Total  19 20.3820    
 
Variate: Plant height at four week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 8.545 2.848 0.76  
Treatments 4 223.570 55.892 15.00 < .001 
Residual 12 44.713 3.726   
Total  19 276.828    
 
Variate: Plant height at six week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 2.538 0.846 0.42  
Treatments 4 401.942 100.486 49.86 < .001 
Residual 12 24.182 2.015   
Total  19 428.662    
 
 
 
129 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Plant height at eight week after transplanting (cm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 171.9 57.3 0.54  
Treatments 4 1200.6 300.1 2.85 0.071 
Residual 12 1264.2 105.3   
Total  19 2636.7    
 
Variate: Stem diameter at four week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 0.4245 0.1415 1.29  
Treatments 4 17.1181 4.2795 38.97 < .001 
Residual 12 1.3178 0.1098   
Total  19 18.8604    
 
Variate: Stem diameter at six week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 1.0080 0.3360 0.50  
Treatments 4 23.3768 5.8442 8.65 0.002 
Residual 12 8.1032 0.6753   
Total  19 32.4880    
 
Variate: Stem diameter at eight week after transplanting (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 25.734 8.578 2.21  
Treatments 4 69.949 17.487 4.50 0.019 
Residual 12 46.582 3.882   
Total  19 142.265    
 
 
 
130 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Bulb sugar content at two weeks after harvesting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 4.226 1.409 1.08  
Treatments 4 90.215 22.554 17.29 < .001 
Residual 12 15.657 1.305   
Total  19 110.098    
 
Variate: Bulb sugar content at four weeks after harvesting 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 3.4095 1.1365 1.73  
Treatments 4 140.7870 35.1967 53.65 < .001 
Residual 12 7.8730 0.6561   
Total  19 152.0695    
 
Variate: Bulb firmness 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 23.742 7.914 1.43  
Treatments 4 56.773 14.193 2.57 0.092 
Residual 12 66.331 5.528   
Total  19 146.846    
 
Variate: Bulb length (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 21.084 7.028 1.16  
Treatments 4 579.880 144.970 23.88 < .001 
Residual 12 72.857 6.071   
Total  19 673.821    
 
 
 
131 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Bulb diameter (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 6.43 2.14 0.19  
Treatments 4 133.17 33.29 2.97 0.064 
Residual 12 134.31 11.19   
Total  19 273.91    
 
Variate: Bulb neck diameter (mm) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 7.266 2.422 0.78  
Treatments 4 266.553 66.638 21.58 < .001 
Residual 12 37.050 3.088   
Total  19 310.869    
 
Variate: Average bulb weight (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 31.46 10.49 0.15  
Treatments 4 1312.71 328.18 4.63 0.017 
Residual 12 849.69 70.81   
Total  19 2193.86    
 
Variate: Rotten bulbs weight at four weeks after harvesting (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 99925 33308 4.34  
Treatments 4 67210 16803 2.19 0.132 
Residual 12 92041 7670   
Total  19 259176    
 
 
 
132 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Healthy bulbs weight at four weeks after harvesting (g) 
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 89283 29761 3.29  
Treatments 4 127721 31930 3.53 0.040 
Residual 12 108649 9054   
Total  19 325653    
 
Variate: Healthy bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 8.9283 2.9761 3.29  
Treatments 4 12.7721 3.1930 3.53 0.040 
Residual 12 10.8649 0.9054   
Total  19 32.5653    
 
Variate: Rotten bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 10.1993 3.3998 4.07  
Treatments 4 6.8530 1.7133 2.05 0.157 
Residual 12 9.1990 0.8363   
Total  19 22.6010    
 
Variate: Total bulbs yield (kg/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 33.146E+07 1.049E+07 0.15  
Treatments 4 1.313E+09 3.282E+08 4.63 0.017 
Residual 12 8.497E+08 7.081E+07   
Total  19 2.194E+09    
 
 
 
133 
 
University of Ghana http://ugspace.ug.edu.gh
Variate: Total bulbs yield (t/ha)  
Source of variation d.f. s.s. m.s v.r. F pr. 
Blocks stratum 3 31.46 10.49 0.15  
Treatments 4 1312.71 328.18 4.63 0.017 
Residual 12 849.69 70.81   
Total  19 2193.86    
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
134 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 10: Color chart guide 
 
 
 
 
 
 
 
 
 
 
135 
 
University of Ghana http://ugspace.ug.edu.gh
Appendix 11: Onion varieties pictures 
ORIENT DAYO TROPHY 
F1 
BAWKU-RED RED-CREOLE 
 
 
 
 
 
 
136