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Horticulture Thesis and Dissertations

2019-12-24

EFFECT OF INTRA-ROW SPACING

AND NITROGEN FERTILIZER RATE

ON GROWTH AND YIELD OF ONION

(Allium cepa L.) UNDER IRRIGATION

CONDITION IN MECHA DISTRICT OF

AMHARA REGION

Dasash, Atalay

http://hdl.handle.net/123456789/10084

Downloaded from DSpace Repository, DSpace Institution's institutional repository

BAHIR DAR UNIVERSITY

COLLEGE OF AGRICULTURE AND ENVIRONMENTAL SCIENCE

DEPARTMENT OF PLANT SCIENCE

M.Sc. PROGRAM IN HORTICULTURE

EFFECT OF INTRA-ROW SPACING AND NITROGEN FERTILIZER RATE ON

GROWTH AND YIELD OF ONION (Allium cepa L.) UNDER IRRIGATION

CONDITION IN MECHA DISTRICT OF AMHARA REGION

M.Sc. Thesis

By

Dasash Atalay Mitiku

October 2019

Bahir Dar, Ethiopia

i

BAHIRDAR UNIVERSITY

COLLEGE OF AGRICULTURE AND ENVIRONMENTAL SCIENCE

DEPARTMENT OF PLANT SCIENCE

M.Sc. PROGRAM IN HORTICULTURE

EFFECT OF INTRA-ROW SPACING AND NITROGEN FERTILIZER RATE ON

GROWTH AND YIELD OF ONION (Allium cepa L.) UNDER IRRIGATION

CONDITION IN MECHA DISTRICT OF AMHARA REGION

M.Sc. Thesis

BY

Dasash Atalay Mitiku

Submitted in Partial Fulfillment of the Requirements for the Degree of Master

of Sciences (MSc.) in HORTICULTURE

Major Advisor: Dr. Melkamu Alemayehu

Co-Advisor: Dr. Semagn Asredie

October 2019

Bahir Dar, Ethiopia

ii

THESIS APPPROVAL SHEET

As member of the board of Examiners of the Master of Science (M.Sc.) open defense exami-

nation, we have read and evaluated this thesis prepared by Dasash Atalay Mitiku “Effect of

Intra-Row Spacing and Nitrogen Fertilizer Rate on Growth and Yield of Onion (Allium

Cepa L.) Under Irrigation Condition in Mecha District of Amhara Region”. We here by

certify that, the thesis is accepted for the fulfilling the requirements for the awarded of the

Degree of Master of Science (M.Sc.) in Horticulture.

Boarder of Examiners

________________________ _______________ ____________

Name of External Examiner Signature Date

________________________ _______________ ___________

Name of Internal Examiner Signature Date

________________________ ______________ ____________

Name of chair Person Signature Date

________________________ ______________ __________

iii

DECLARATION

This is to certify that, this thesis entitled “Effect of Intra-Row Spacing and Nitrogen Ferti-

lizer Rate on Growth and Yield of Onion (Allium Cepa L.) Under Irrigation Condition in

Mecha District of Amhara Region” submitted in partial fulfillments for the award of the

degree of Master of sciences (M.Sc.) in Horticulture to the graduate program of College of

Agriculture and Environmental Sciences, Bahir Dar University by Ms. Dasash Atalay is an

authentic work carried out by her under our guidance. This thesis has not been submitted to

any other institution earlier for the award of any academic degree, diploma to the best of our

knowledge.

Name of the Student

Dasash Atalay Signature ____________ Date ________________

Name of Major Advisor

Dr. Melkamu Alemayehu Signature_____________ Date ________________

Name of Co- Advisor

Dr. Semagn Asredie Signature _____________ Date ______________

iv

ACKNOWLEDGEMENTS

First, I would like to offer lots of thanks to God and his mother Saint Virgin Mary for their

compassionate help in all aspects of my life. It is my pleasure to express my heartfelt appreci-

ation and deepest gratitude to my major advisor, Dr. Melkamu Alemayehu and my co-advisor

Dr. Semagn Asredie for their useful comments, as well as for guiding and supervising my

work during the entire period of the research and for shaping the final write-up of the thesis.

Further, I also extend my gratitude towards the Assosa University for granting me a scholar-

ship for my graduate study and to Bahir Dar University for hosting me.

My sincere acknowledgment is also extended to Adet Agricultural Research Center for

providing me tools and equipment’s that were required to accomplish the research work. Last-

ly and most importantly, my heartfelt thanks go to my classmates Mequannet Tilahun and

Eden Melaku and my beloved for their support and encouragement throughout the entire peri-

od of my study.

v

DEDICATION

I dedicate this thesis work to my mother, my beloved and respected families for their affection

and consistent care in the success of my life.

vi

ABBREVIATIONS AND ACRONOMY

AARC Adet Agricultural Research center

ANOVA Analysis of variance

CIMMYT International Maize and Wheat Improvement center

CSSE Crop Science Society of Ethiopia

CSA Central Statistical agency

EARO Ethiopian agricultural research Organization

EIAR Ethiopian Institute of agricultural research

FAO Food and Agricultural Organization

FAOSTAT Food and Agricultural Organization Statics

LSD Least Significance difference

MoARD Ministry of Agriculture and rural development

RCBD Random complete Block design

SAS Statistical application of science

SNNPRS Southern Nation, Nationalities and Peoples Regional state

EARO Ethiopian agricultural research Organization

vii

EFFECT OF INTRA-ROW SPACING AND NITROGEN FERTILIZER RATE ON

GROWTH AND YIELD OF ONION (Allium cepa L.) UNDER IRRIGATION CONDI-

TION IN MECHA DISTRICT OF AMHARA REGION

By

Dasash Atalay Mitiku

Major Advisor: Dr. Melkamu Alemayehu

Co-Advisor: Dr. Semagn Asredie

ABSTRACT

Onion is an important cash crop produced by smallholder farmers in Amhara Region. The

productivity of the crop is however low which is among others associated with Poor soil fertility management practice coupled with under optimum plant population. Moreover, farm-

ers are complaining where the present recommended 10 cm intra row spacing produces large sized bulbs, which are not preferred by consumers for home consumptions. Therefore, the present study was initiated with the objective of investigating the effects of intra row- spacing

and nitrogen fertilizer rates on growth and yield of onion. The treatments consisted of four levels of Nitrogen fertilizer rate (0, 41, 82, 123 kg ha-1 N) and three-intra row spacing (4, 7.

10 cm). The experiment was down in Randomized Complete Block Design (RCBD) in factori-al arrangement with three replications. Date on Growth, yield and yield components of onion were collected and subjected to ANOVA using SAS (version 9.0) software. Both the main ef-

fect as well as the interaction effect of intra row spacing and rates of nitrogen fertilizer signif-icantly influenced almost all the tested growth and yield components of onion. The highest

significant plant height (60.53cm), leaves number per plant (14.10cm), leaves length (60.90cm), day to maturity (115 days) and bulb weight (96.05 g) were recorded from onion plants supplied with 82kg ha-1 N and 123 kg ha-1 N both combined with 10 cm of intra row

spacing. The highest marketable bulb yield (43.80 t/ha) was recorded from treatment combi-nation of 82 kg ha-1 N and 4 cm of intra row spacing. Onion plants without nitrogen fertilizer

application and narrow intra row spacing were inferior in almost all growth and yield com-ponents. Based on the results of the present study, the combination of 82 kg ha-1 N and 4 cm of intra row spacing can be recommended for economical production of onion in the study

area since it recorded the highest net benefit with acceptable marginal rate of return. Since the results are limited to one season and location, it is advised to repeat the experiment in

different area and season for forceful recommendations.

Keywords: Bombay Red Variety, Koga Irrigation Scheme, Marketable and Total Bulb

Yield

viii

Table of contents

Contents Pages

THESIS APPPROVAL SHEET.......................................................................................................ii

DECLARATION ............................................................................................................................ iii

ACKNOWLEDGEMENTS ............................................................................................................iv

DEDICATION ................................................................................................................................ v

ABBREVIATIONS AND ACRONOMY.......................................................................................vi

ABSTRACT ..................................................................................................................................... vii

Table of contents .................................................................................................................. viii

Lists of Tables .................................................................................................................................xi

List of Figures ................................................................................................................................ xii

List of Appendices ........................................................................................................................ xiii

Chapter 1. INTRODUCTION ......................................................................................................... 1

1.1. Background and Justification ............................................................................................... 1

1.2. Statement of the Problem ..................................................................................................... 3

1.3. Objectives of the Study’s ..................................................................................................... 5

1.3.1. General objective........................................................................................................... 5

1.3.2. Specific objectives......................................................................................................... 5

Chapter 2. LITERATURE REVIEW ............................................................................................. 6

2.1. Origin and Distribution of Onion ......................................................................................... 6

2.2. Ecological Requirement of Onion........................................................................................ 7

2.3. Importance and Production of Onion in Ethiopia ................................................................ 7

2.4. Potentials and Constraints of Onion Production in Ethiopia ............................................... 8

2.5. Effects of Nitrogen on Growth and Yield of Onion............................................................. 9

ix

2.6. Effect of Plant Spacing on Onion Growth and Yield of Onion ......................................... 11

2.7. Interaction Effect of Nitrogen and Plant Spacing on Growth and Yield of Onion ............ 11

Chapter 3: MATERIAL AND METHODS ................................................................................. 13

3.1. Description of Study Area.................................................................................................. 13

3.2. Experimental Materials, Treatments and Design ............................................................... 14

3.3. Experimental Procedure ..................................................................................................... 15

3.4. Methods of Data Collection ............................................................................................... 18

3.4.1. Growth parameters of onion........................................................................................ 18

3.4.2. Yield related parameters of onion ............................................................................... 19

3.5. Methods of Data Analysis .................................................................................................. 19

3.6. Soil sampling of experimental plots................................................................................... 20

Chapter 4. RESULTS AND DISCUSION .................................................................................... 22

4.1. Effects of Nitrogen Fertilizer and Intra-row Spacing on Growth of Onion ....................... 22

4.1.1. Days to maturity .......................................................................................................... 22

4.1.2. Plant height.................................................................................................................. 23

4.1.3. Leaf number per plants................................................................................................ 24

4.1.4. Leaf Length ................................................................................................................. 25

4.2. Effects of Nitrogen Fertilizer and Intra-row Spacing on Yield Component of Onion....... 27

4.2.1. Bulb diameter .............................................................................................................. 27

4.2.2. Bulb weight ................................................................................................................. 28

4.2.3. Bulb size distribution of onion .................................................................................... 31

4.2.4. Marketable bulb yield.................................................................................................. 36

4.2.5. Unmarketable bulb yield ............................................................................................. 37

4.2.6. Total Bulb Yield.......................................................................................................... 38

4.3. Correlation Analysis of Growth and Yield Parameters as Influenced by Intra row

Spacing and Nitrogen Fertilizer ................................................................................................ 42

4.4. Economic Analysis............................................................................................................. 44

x

Chapter 5: CONCLUSION AND RECOMMENDATIONS ........................................................ 49

5.1. Conclusions ........................................................................................................................ 49

5.2. Recommendations .............................................................................................................. 50

REFFERENCES............................................................................................................................ 51

APPENDICES............................................................................................................................... 62

BIOGRAPHY.................................................................................Error! Bookmark not defined.

xi

Lists of Tables

Table 3.1: Treatment combinations used in the study.............................................................. 15

Table 3.2: Major physic-chemical properties of the experimental soil before planting .......... 21

Table 4.1: Main effect of nitrogen rates and intra-row spacing on growth of onion at Koga

Irrigation Scheme during the (2018) irrigation season............................................................. 26

Table 4.2: Interaction effects of intra-row spacing and nitrogen fertilizer levels on Growth of

onion plants .............................................................................................................................. 27

Table 4.3: Main effects of intra-row spacing and nitrogen on diameter and weight of onion

bulbs ......................................................................................................................................... 30

Table 4.4: Interaction effect of intra-row spacing and nitrogen fertilizer levels on diameter and

Weight of onion bulb................................................................................................................ 31

Table 4.5: Main effect of intra-row spacing and nitrogen fertilizer rates on bulb-size

distribution of onion ................................................................................................................. 35

Table 4.6: Interaction effect of intra-row spacing and nitrogen fertilizer levels on Bulb-size

Distribution of onion ................................................................................................................ 36

Table 4.7: Main effects of intra-row spacing and nitrogen fertilizer on bulb yield of onion at

Koga Irrigation Scheme during the (2018) irrigation season ................................................... 40

Table 4.8: Interaction effect of intra-row spacing and levels of nitrogen fertilizer on yield of

onion at Koga Irrigation Scheme during the (2018) irrigation season ..................................... 41

Table 4.9: Simple correlation between growth and yield components of onion as influenced

by intra row spacing and rate of nitrogen................................................................................. 44

Table 4.10: Economical analysis for marketable yield of onion as affected by nitrogen

fertilizer rate and intra-row spacing ......................................................................................... 46

Table 4.11: Dominance analysis for marketable yield of onion as affected by nitrogen

fertilizer and intra-row spacing ................................................................................................ 47

Table 4.12: Marginal rate of return (MRR) of marketable onion yield as affected by nitrogen

fertilizer and intra-row spacing ................................................................................................ 48

xii

List of Figures

Figure 3. 1: Map of the study area Mecha district ........................................................................ 13

xiii

List of Appendices

Appendix 1: Mean squares of analysis of variance for plant height (PH), leaf length (LL), leaf

number per plant (LN), day to maturity (DM) ......................................................................... 62

Appendix 2: Mean squares of analysis of variance for yield and yield related traits of onion 63

Appendix 4: Mean squares of analysis of variance for marketable and unmarketable size

distribution of onion ................................................................................................................. 63

Appendix 5: Mean squares of analysis of variance for marketable bulb yield, unmarketable

bulb yield and total yield of onion ........................................................................................... 64

1

Chapter 1. INTRODUCTION

1.1. Background and Justification

Onion (Allium cepa L.) belongs to the family Alliaceae is an important vegetable bulb crop

cultivated in tropical and subtropical parts of the world, which ranks second next to tomato

(FAO, 2012). The crop is grown in at least 261 countries of the world (FAOSTAT, 2017). In

Ethiopia, onion is one of the most cool season bulb vegetables produced by smallholder farm-

ers mainly as as a source of cash income (Lemma Dessalegn and Shimeles Aklilu, 2003).

Onion contributes a significant nutritional value to the human diet and has medicinal proper-

ties. The crop primarily consumed for its unique flavor or ability to enhance the flavor of oth-

er foods (Randle and Ketter, 1998). All the plant parts are edible, but the bulbs and the lower

stem sections are the most popular as seasoning or as vegetables in stews (MoARD, 2009). It

is one of the richest sources of flavonoids in the human diet and flavonoid where its consump-

tion has been associated with a reduced risk of cancer, heart disease and diabetes. Flavonoids

are not only anti-cancer, but also known to be anti-bacterial, antiviral, anti-allergenic and anti-

inflammatory. Quality parameters of onion bulb have become important to meet demands of

both processing and fresh market buyers (Brewster, 1990 and Pelter et al., 2004).

According to FAOSTAT (2017), 97,862,928 tons of onion yields were produced on 5201591

hectares across the world. China and India are the leading onion producing countries contrib-

uted 26.3% and 22.6% of the total world onion production respectively (FAOSTAT, 2014). In

terms of productivity however, USA is the first country in the world with 54.6 t/ha followed

by Netherland (49.7 t/ha), Egypt (33.7 t/ha) and Iran (31.8 t/ha) (FAOSTAT, 2014). The pro-

duction of onion in Africa is very low as compared to the world. As statistics showed,

12,174,553 tons of onion yields were produced in area coverage of 1114907 hectares with av-

erage productivity of 11.4 t/ha (FAOSTAT, 2017).

Onion was introduced to the agricultural community of Ethiopia in the early 1970’s when for-

eigners brought it in (Tadesse Adgo, 2008). Though shallots are traditional crop in Ethiopia,

Onion is becoming more widely grown in recent years.

2

Currently, the crop is producing in different parts of the country for local consumption (Lem-

ma Dessalegn and Shimeles Aklilu, 2003). It is considerably important in the daily Ethiopian

diet.

Vegetables including onion are producing in many home-gardens and in some extent com-

mercially in different parts of Ethiopia. The major producers are however, the small-scale

farmers using mainly rainfall although some produced using irrigation (CSA, 2016). The av-

erage productivity of onion in Ethiopia is about 10.06 t/ha (FAOSTAT, 2017) which is very

low compared to world`s average of 18.81 t/ha (FAOSTAT, 2017). Amhara region contrib-

utes for production of onion in the country by constituting the estimated area coverage of

12,262.79 hectare with average productivity of of 11.6 t/ha (CSA, 2016).

The production and productivity of vegetables in particular onion is very low in Ethiopia alt-

hough the country has huge potentials to the crop production and utilization. Several factors

contribute to this low level of production and productivity. Among these, lack of appropriate

agronomic packages, shortage of seeds of improved varieties, diseases, insect pests and poor

extension services, high costs of chemical fertilizers and sometimes their unavailability to

small-scale farmers (Currah and Proctor, 1990, Melkamu Alemayehu et al., 2015).

The use of appropriate agronomic and management practices play a key role in increasing

crop yields including onion. Optimum agronomic and management practices for a crop varies

with plant population, planting, and harvesting dates and fertilizers used, with the prevailing

environmental conditions (soil fertility, rainfall, etc), purpose of production of the crop and

even within cultivar.

Maintaining adequate level of soil fertility is recognized as one of management practices that

affect growth, development and yield of plants including onion (Tisdale Sintayehu et al.,

1995). One of the options to maintain soil fertility as well as to obtain higher yield is the ap-

plication of inorganic fertilizers. According to Shaheen et al. (2007), onion is a heavy feeder

of mineral elements. A crop of 35 t/ha removes approximately 120 kg N, 50-kg P2O5 and 160-

kg K2O per hectare (Mohanty et al., 2015). Hence the greater its ability to utilize nutrients for

crop production, the greater is the yield potential.

3

Because of their shallow and unbranched root system, onions are the most susceptible crop

plants in extracting nutrients. Hence, they require and often respond well to addition of ferti-

lizers (Brewster, 1994; Rizk et al., 2012). Therefore, optimum fertilizer application and culti-

vation of suitable varieties with appropriate agronomic practices in specific environment are

necessary for obtaining good yield of onion.

In addition to nutrients, plant spacing is an important factor determining onion yield and qual-

ity. An essential aspect of any crop production system is the development of a crop canopy

that optimizes the interception of light, photosynthesis, and the allocation of dry matter to

harvestable parts. Manipulating row spacing and plant population influences crop canopy. As

plant density increases, yield per unit area up to certain level increases. Further increasing of

plant density, yield per unit area declines since yield per plant tends to decrease because of

competition for growth factors between adjacent plants (Silvertooth, 2001). Planting density

greatly influence texture, quality, taste and yield of onion even within a particular variety

(Saud et al., 2013).Thus, spacing is an important factor for the production of onion since it

affects both bulb yield and quality.

1.2. Statement of the Problem

Onion is one of the most important vegetable crops cultivated mostly under irrigated condi-

tion in Mecha district in West Gojam Zone of Amhara Region. However, the crop productivi-

ty is remained very low compared to the world average (Yemane Kahsay et al., 2016). The

low level of vegetable production in general and that of onion in particular is associated with

poor agronomic practices, shortage of seeds of improved varieties, diseases and insect pests,

poor extension services, high costs of agricultural chemicals including fungicides, insecticides

and fertilizers ( Melkamu Alemayehu et al., 2015; Nigatu Muluneh, 2016). Moreover, quality

and yield of particular onion variety are greatly affecting planting density even if grown in the

same environment (Fahad et al., 2013).

Mineral fertilizers are one of the principle factors that materially set up onion growth and pro-

duction. However, due to ever increasing prices, smallholder farmers may not apply full dose

of inorganic fertilizers which are required to sustain and increase yields (Takashi and Ayumi,

2010; Negasi Tekeste et al., 2013).

4

At present, onion growers in the study area produce onion with the application of nitrogen

fertilizer rates and intra-raw spacing which they feel as best for obtaining higher yields of on-

ion crop (Personal communication). However, the blanket recommended rates of fertilizers

are 200 kg ha-1 of DAP and 100 kg ha-1 Urea (Nikus Olani and Mulugeta Fikre, 2010).

Plant density is another important appropriate management area for onion production. Opti-

mum plant spacing enables the farmer to keep optimum plant population, avoid over and less

population in a given plot of land, which has negative effect on growth, yield and quality

(EARO, 2004). To avoid nutrient competition sufficient spacing between plants and rows is

vital to get maximum yield of onion in a given land. The optimum use of spacing or plant

population has dual advantages. It avoids strong competition between plants for growth fac-

tors such as water, nutrient and light. In addition, optimum plant population enables efficient

use of available cropland without wastage (Geremew Awas et al., 2010).

The recommended spacing for production of onion is however 40 cm x 20 cm x 10 cm in

Ethiopia (Lemma Dessalegn and Shimeles Aklilu, 2003). However, wider plant spacing pro-

duced the large size of bulbs; the large size of bulb contains highest water and has more sur-

face area per unit of bulb there by highest rate of transpiration and then highest weight loss.

Sing and Sing (2003) reported that, large size of bulb exhibited the highest weight loss com-

pared to smaller size of bulbs.

Recently research results confirmed that spacing of 10 cm between plants produced large bulb

size. Hence, individual consumers do not prefer these large sized bulbs for home consumption

(EHDA, 2011; Habtamu Tegen et al., 2016). For example, Geremew Awas et al. (2010) rec-

ommended intra row spacing of 4 cm for ‘Adama’ Red varieties, and 6 cm for ‘Bombay’ Red

variety, in central rift valley areas of Ethiopia. According to Yemane Kahsay et al. (2013), at

wider intra row spacing (10 cm) produces big size bulb which are liable to highest rotting per-

centage compared those produced with intra-row spacing (5 and 7.5 cm). Bosekeng (2012)

also observed that large plants grown at wider spacing are associated with split bulbs and sen-

sitive to a cold stimulus causing bolting. Optimization of Plant population is thus important

and needs to be optimized. Therefore, the present study was proposed to evaluate the effects

of spacing and nitrogen fertilizer on growth and yield of onion.

5

1.3. Objectives of the Study’s

1.3.1. General objective

The general objective of the present study was contributing towards the improvement of pro-

duction and productivity of onion in the study area through optimizing plant spacing and ni-

trogen fertilizer rate.

1.3.2. Specific objectives

The specific objectives of the study were to asses:

Effect of intra -row spacing and nitrogen fertilizer rate on growth and yield of onion;

and

Determine the optimum intra- row spacing and nitrogen fertilizer rate for economical

production of onion at Koga irrigation Scheme.

6

Chapter 2. LITERATURE REVIEW

2.1. Origin and Distribution of Onion

The primary origin of onion is Central Asia with secondary center in Middle East and Medi-

terranean Region (Zohary and Hopf, 2000, Grubben and Denton, 2004). Onion is a herba-

ceous monocot plant, which is cultivated as an annual crop for the purpose of bulb production.

However, it is cultivated as biennial crop for seed production. During the first season, bulbs

are formed while flower stalks and seeds are developed in the second season (Corgan et al.,

2000. Onion belongs to the genus Allium of the family Alliaceae (Hanelt, 1990). It is a cross-

pollinated crop having diploid chromosomes number (2=16 (Bassett, 1986). Recent estima-

tions accept about 750 species in the genus Allium, among which onion, Japanese bunching

onion, leek and garlic are the most important edible Allium crops (Rabinowitch and Currah,

2002).

Jones and Mann (1963) gave simple classification of the genus where Allium cepa L. is cate-

gorized into common onion group, aggregatum group or shallots and ever-ready onion. From

horticulture, point of view common onion group is the most important and widely produced

group worldwide. The onion bulb is composed of fleshy enlarged leaf base or scale (Shanmu-

gasundaram and Kalib, 2001). Onion roots are short lived, being continuously produced, rare-

ly have branches and root hairs, and rarely increase in diameter. The terminal inflorescences

develops from the ring like apical meristem scapes and several, generally elongate well above

the leaves and ranges in height from 30 to more than 100 cm (Brewster, 1994;

Shanmgasundaram and Kalib, 2001).

Onion has its own distinctive flavor, pungency, is eaten as fried, boiled, roasted or raw in sal-

ad as vegetable, and is widely used as a condiment in preparation of soups, savory dish,

canned food product, salads and sandwiches. Moreover, it is also processed as pickle, chut-

ney, and sauces and consumed in dehydrated form (Muhammad S. J, 2004).

7

2.2. Ecological Requirement of Onion

Onion can grow between 500 and 2400 meter above sea level. Nevertheless, according to

Lemma Dessalegn and Herath (1994), the best growing altitude in Ethiopia is between 700

and 1800 m above sea level.

Onion crop can be successfully produced on most fertile soils. The onion crop requires alluvi-

al or sandy loam soli with high levels of organic matter for optimum vegetative growth. The

onion crop is gross feeder since they require high fertile soil to maintain maximum yields

(Brewster, 1999). The favorable pH for onion production ranges from of 6.2 to 6.8. However,

onion crop may also grow on relatively acidic soils (Karim and Ibrahim, 2013). According to

Karim and Ibrahim (2013), onion yields however severely reduced in soil salinity.

Temperatures around 20 –22oC are favorable for vegetative growth while temperatures around

12oC favor seed stalk formation (Sukprakarn et al., 2005). According to CSSE (2006), the di-

verse agro-climatic conditions that prevailed in Ethiopia generally provide the opportunity to

produce bulbs and seeds of onion for local use and export market.

2.3. Importance and Production of Onion in Ethiopia

The production of vegetables including onion is an important sector of horticulture. Its pro-

duction is in increasing trend, which is associated with the expansion of irrigated agriculture.

The sector is an important source of income, row material for industry, employment oppor-

tunity and improvement of food security as indicated by (Lemma Dessalegn et al., 2006). On-

ion contributes substantially to the national economy, apart from overcoming local demands.

It is used almost daily as a spice and vegetable in the local dish regardless of religion, ethnici-

ty, and culture (CSSE, 2006). It has distinctive flavor, pungency, is eaten as fried, boiled,

roasted or raw in salad as vegetable, and is widely used as a condiment in preparation of

soups, savory dish, canned food product, salads and sandwiches. Moreover, it is also pro-

cessed as pickle, chutney, and sauces and consumed in dehydrated form (Muhammad S. J,

2004).

Onion is producing on small and large scale in Ethiopia. It occupies an economically im-

portant place among vegetables in the country. The crop is produced commonly under rain-

8

fed season and under irrigation in the offseason. However, the offseason crop (under irriga-

tion) constitutes much of the area under onion production. In Ethiopia, onion production area

is growing from time to time which is associated with its high productive and cost-effective

per unit area, ease of production and the increases in small-scale irrigation areas (Lemma

Dessalegn and Shimeles Aklilu, 2003). The main onion producing regions are Amhara, Tig-

ray, Oromia, Benishngule-Gumuz, Gambella and South Nation Nationalities and Peoples Re-

gions (CSA, 2016).

2.4. Potentials and Constraints of Onion Production in Ethiopia

Ethiopia including Amhara Region has diverse agro-ecologies that enable the country to pro-

duce tropical, subtropical and temperate vegetables including onion throughout the year

(Kubsa A. et al., 2006). The country has a great potential to produce onion throughout the

year both for local consumption and for export because of presence of underground and sur-

face water potential, which can be used, for the production of horticultural crops including

onion (Selesh Bekele, 2010). Moreover, the Ethiopian Agricultural Research Institute has

made efforts towards improvement of varieties and released different improved varieties in-

cluding Adama Red, Bombay Red, Red Creole, Melkam, Mermiru Brown, Nasik Red and

Nafis (Lemma Dessalegn and Shimelis Aklilu, 2003; MoARD, 2010). Onion is therefore pop-

ular over the local shallot, which is low in its productivity (Lemma Dessalegn, 2004).

The production and efficiency of horticultural crops including onion is significant poorer than

other African countries. Generally, in Ethiopia, as well as in Amhara Region the production of

onion is very low due to insufficient availability of quality seeds, technologies used and inap-

propriate cultural practices (Nikus Olani and Fikre Mulugeta, 2010). In addition to this, since

most of the time onion is produced by smallholder farmers, appropriate agronomic practices

employed agricultural inputs such as fertilizers, improved varieties and pesticides are not suf-

ficiently used, and inappropriate postharvest handling practices are done. Generally, farmers

produce horticultural crops with traditional farming system that leads to low production and

productivity (Melkamu Alemayehu et al., 2015).

Moreover, the production of horticultural crops is dependent on natural rainfall and therefore

their production is totally influenced by rainfall fluctuation, Like to other horticultural crops,

9

onion is produced by traditional farming practices where the farmers lack improved onion

production technologies. Improved onion seeds are inadequate because of lack of seed pro-

duction system in the region. Fertilizers are mostly available for main season crops while for

irrigated vegetable crops like onion, fertilizers are not available in sufficient quantity

(Melkamu Alemayehu et al., 2015).

Furthermore, due to favorable tropical conditions in Ethiopia, which favor the development of

pests, onion is suffering from various diseases and insect pests throughout the country includ-

ing in Amhara Region. The most common diseases occurred in Ethiopian onion farms are

purple blotch, onion neck rot and powdery mildew, which are caused by the fungi Alternari-

aporri, Botrytis cineraria and Peronospora destructor, respectively (Lemma Dessalegn and

Shimelis Aklilu, 2003). Among insect pests, thrips, mites and cutworms are the most im-

portant once in farmer`s onion farms (Lemma Dessalegn, 2004). The damages caused by pests

are further interested because most onion-growing farmers do not use the exact pesticides and

the recommended rates for the control of pests. Some traders mix pesticides with other sub-

stances (adulteration) which may either reduces their effectiveness or damage the crop plants

and sosustain economic losses for onion growing farmers (Edossa Etissa, 2013).

Poor infrastructures such as rural roads and communication for efficient flow of goods and

market information are limited, where most onion production sites are not accessible for

transportation. As onions are perishable by nature, they cannot be stored for long period with-

out quality decline unless properly handled. Moreover, there is a serious problem in the mar-

keting of horticultural crops including onion in Ethiopia in general and in Amhara region in

particular which affect not only the incomes negatively but also the interests of farmers to par-

ticipate in the onion production in the following years (Melkamu Alemayehu et al., 2015).

2.5. Effects of Nitrogen on Growth and Yield of Onion

Nitrogen often refers as primary macronutrients because of the probability of plants being de-

ficient in this nutrient and the large quantities taken up from the soil relative to other essential

nutrients (Marschner, 1995). Nitrogen comprises 7% of total dry matter of plants and is a con-

stituent of many fundamental cell components (Bungard et al., 1999). The amount of nitrogen

needed is usually based on soil organic matter content, crop uptake and yield levels. Nitrogen

10

uptake levels by onion crops may vary from less than 50 kg to more than 300 kg per hectare,

depending on cultivar, climate, plant density, fertilization, irrigation efficincy and yield levels

(Sorensen, 1996; Suojala et al., 1998).

Nitrogen plays an important role in the growth and development of plants including onion. A

good supply of nitrogen stimulates root growth and development as well as the uptake of oth-

er nutrients (Brady and Weil, 2002). Under sub-optimal supply of nitrogen, onions could be

severely stunted, with small bulb size then reduced marketable yields. By contrast, too much

nitrogen could result in excessive vegetative growth, delayed maturity, increased susceptibil-

ity to diseases, reduced dry matter contents and storability and, thus, result in reduced yield

and quality of marketable bulbs (Brewster, 1994; Sørensen & Grevsen, 2001).

Nitrogen significantly affected plant height, number of leaves, fresh weight, diameter, length

and weight of bulb as well as bulb yield of onion (Nasreen et al., 2007; Al-Fraihat, 2009 and

EI-hamady, 2017). Moreover, fertilization of onion plants with nitrogen fertilizer extended the

number of days required for onion crop to attain its physiological maturity. In this regard, Ab-

dissa Yadeta et al. (2011) reported that nitrogen fertilization extended physiological maturity

by about 6 days over the unfertilized plants regard less of its rate. Morsy et al. (2012) also re-

ported that maturity of onion plants was delayed in response to increasing nitrogen applica-

tion.

Morsy et al. (2012) reported that onion plant height was significantly increased as increased

nitrogen fertilizer rates. The increase in plant height with the addition of higher nitrogen ferti-

lizer level could be attributed to more availability of the nutrient, which enhances protein syn-

thesis that lead to increased accumulation of carbohydrates, which in turn, may result in in-

creased plant growth such as leaf number and leaf length (Rizk, 2012; Marschner, 1995). Sim-

ilarly, various researchers reported that higher nitrogen fertilization increased leaf length and

marketable yield of onion (Balemi et al., 2007; Soleymani and shahrajabian, 2012; Rao et al.,

2013). However, the yield of any crop including onion depends on the optimum level of plant

nutrients in the soil (Tisdale Sintayehu et al., 1995).

11

2.6. Effect of Plant Spacing on Onion Growth and Yield of Onion

Plant population refers to number of plants per unit area. It is important in onion production

since it influence growth, yield and quality of onion bulbs (Brewster, 1994). Plant population

affects interplant competition towards the growth factors like water, nutrient and light, which

influences growth and development of plant. According to Khan et al. (2002), wider intra row

spacing significantly recorded taller plant height as compared to narrow intra-row spacing.

Similarly, Demes Rahel (2018) reported that Leaf length increased as intra-row spacing ex-

panded from 7 to 13 cm.

Similarly, Kantona et al. (2003); Aliyu U. et al. (2008) and Jilani et al. (2009) also reported

that taller onion plants were recorded at wider spacing than narrower spacing where narrower

spacing leads to stiffer competition among plants for growth factors.

According to Sikder et al. (2010), higher leaf numbers per plant of onion was recorded in re-

sponse to wider plant spacing. Intra row spacing also influenced the yield of onion. He also

reported that wider intra row spacing gave higher total dry biomass of onion recorded as com-

pared to narrower spacing. Additionally, Mahadeen (2008) reported that maximum marketa-

ble bulb yields were recorded at lower intra-row spacing compared to wider spacing. Similar-

ly, Coleo et al. (1996) reported the highest commercial bulb yield at higher planting density,

while the highest proportion of large sized bulbs were recorded at lower planting density.

2.7. Interaction Effect of Nitrogen and Plant Spacing on Growth and Yield of Onion

The amount of nitrogen to apply depends on the various factors including the fertility of the

soil, environmental conditions and the type and density of crops planted. Reports of research-

ers indicated that the interaction effect of intra-row spacing with the amount of nitrogen ferti-

lizer applied where highest spacing in association with higher nitrogen level increased number

leaves per plant and spitted bulbs (Islam et al., 1999; Pervez et al., 2004). Application of

higher rate of nitrogen at wider spaced plants increased number of leaves per plants of onion

(Shojaei et al., 2011).

According to Naik and Hosamani (2003), maximum bulb yield of onion was recorded at nar-

row spacing while wider intra row spacing decreased bulb yield.

12

The combination of closer intra row spacing and higher levels of nitrogen recorded the high-

est bulb yield. On the other hand, onion plants spaced at wider intra row spacing recorded

highest bulb diameter of onion plants compared to narrow spaced once. Similarly, increased

in nitrogen levels increased diameter and average weight of onion bulbs (Naik and Hosamani,

2003). Shojaei et al. (2011) also reported that plants, supplied with higher rate of nitrogen and

planted at lower population density, produced highest mean bulb weight. Based on

Weldemariam Seifu et al. (2015) reports, the longest leaf number per plan was obtained with

the application of N at the rate of 138 kg ha-1 while the shortest plant leaf was observed in the

control plots.

13

Chapter 3: MATERIAL AND METHODS

3.1. Description of Study Area

The study was conducted at Koga Irrigation Scheme during the irrigation season of 2018 in

Mecha district of Amhara Region, Northwester Ethiopia. The district is located in West

Gojam zone of the Amhara Region. Koga irrigation scheme is found about 35 km far to

Southwest of Bahir Dar, Capital city of Amhara Regional State. It is located at 11O 10′N to

11O 25′N latitude and 37O 02′E to 37O 17′E longitude with and with an elevation of 1960

m.a.s.l. According to Bahir Dar Meteorology station (unpublished), the study area received an

annual mean rain fall of 1395.23 mm. The mean maximum and minimum temperature of the

study area 270C and 12.80C respectively. Major crops grown in Koga Irrigation Scheme in-

cludes, maize, finger millet, bread wheat and teff during the main cropping season while;

bread wheat, potato, onion, tomato and cabbage during the irrigation season (Melkamu Ale-

mayehu et al., 2015).

Figure 3. 1: Map of the study area Mecha District

14

3.2. Experimental Materials, Treatments and Design

Bombay Red variety of onion was used as a test crop, which was collected from Adet Agri-

cultural Research Center (AARC). The variety is released by Melkasa Agricultural Research

Center (EARO, 2004), for its high yielding and promising agronomic performances. It is an

early maturing variety, takes less than 120 days to maturity (EARO, 2004). The cultivar is

well adapted to the experimental areas and preferred by smallholder farmers in the locality as

well as by commercial farmers throughout the country. The variety can be grown in the areas,

which have an altitude of 700-1800 m.a.s.l.

A field experiment was conducted on 3x4 factorial arrangement of different intra row spacing

(4cm, 7cm, 10cm) and nitrogen fertilizer rates (0kg, 41kg, 82kg, 123kg/ha) totally 12 treat-

ments with three replications. The experiment was laid out in Randomized Complete Block

Design (RCBD) with three replications and there could be 36 plots. The size of each plot was

2mx1.8m, which accommodates different net plot areas. The distance between furrow, blocks

and plots was 40 cm, 1.5 m and 1 m respectively. All other agronomic management activities

except intra row spacing and nitrogen fertilizer such as cultivation; weeding, plant protection

and ridging were practiced uniformly in all plot of the experiment as per the recommendation

(Lemma Dessalegn and Shimeles Aklilu 2003).

15

Table 3.1: Treatment combinations used in the study

Treatments number Intra row-spacing (cm) Nitrogen rate (kg) Treatment combinations

1

2

3

4

4

0

41

82

123

T1= 4cm x 0kg ha-1

T2= 4cm x 41kg ha-1

T3= 4cm x 82kg ha-1

T4= 4cm x 123kg ha-1

5

6

7

8

7

0

41

82

123

T5= 7cm x 0kg ha-1

T6= 7cm x 41kg ha-1

T7= 7cm x 82kg ha-1

T8= 7cm x 123kg ha-1

9

10

11

12

10

0

41

82

123

T9= 10cm x 0kg ha-1

T10= 10cm x 41kg ha-1

T11= 10cm x 82kg ha-1

T12= 10cm x 123kg ha-1

3.3. Experimental Procedure

Good quality seeds of Bombay Red variety of onion was sown in rows on 1m x 5m well pre-

pared seedbed at seeding rate of 3-4 kg/ha to raise seedlings (EIAR, 2012). The management

of seedlings such as watering, cultivation, fertilization, control of diseases and insect pests

were done as per the recommendation as described by EARO (2004).The experimental site

was prepared well by broken down large clods in order to make the fine tilth of the experi-

mental plots. The whole field was divided in to three blocks containing twelve (12) plots. The

plots were leveled and prepared with a distance of 1 m between plots, 1.5 m between blocks

and 40 cm between furrows. Each of the twelve-treatment combination was assigned to the

experimental plots with three replications.

After 55 days of sowing, seedlings which have 3 to 4 true leaf stage with 12-15 cm height,

healthy and vigorous seeding were transplanted on well prepared experimental plots where

they were plowed and harrowed using oxen. Replanting of dead seedlings in the field was

done one week after transplanting on the place where the first first seedlings were planted.

18

Urea and Diammonium Phosphate (DAP) and Triple Super Phosphate in the form of (P2O5)

for (control) were supplied as a source of nitrogen and phosphorus respectively. However,

Diammonium Phosphate (DAP) was applied uniformily for all plots except (control) at the

time of transplanting. The recommended rate of urea (46%N) was applied to onion plants in

two equal splits where one half was applied at 25 days after transplanting and the remaining

one half after 45days of transplanting as recommended by (EARO, 2004).

Experimental units were irrigated using furrow irrigation method in each plot and row in plots

received water from the source without passing any of the experimental plots to prevent mix-

ing of fertilizer rates agreed to different plots. Transplanted seedlings were irrigated using fur-

row irrigation at 4-5 days interval until their establishment and at 5-7 days intervals until ma-

turity. Fifteen days before harvesting however, irrigation of plants was stopped for curing

purpose as recommended by Nigus Olani and Mulugeta Fikrie (2010).

3.4. Methods of Data Collection

3.4.1. Growth parameters of onion

Days to 80% maturity ( days):- The number of days elapsed from the time of transplanting

up to the date when 80% of plants became dry and collapsed at the neck was counted and the

mean values were computed and used for further analysis as indicated by Guesh Tekle, (2015)

and Nigatu Muluneh, (2016).

Plant height (cm):- Plant heights from the soil surface to the longest leaf of ten randomly se-

lected plants grown in the net plot area were measured using a ruler at physiological maturity

and the mean values were computed and used for further analysis.

Number of leaves/plant (count):- The numbers of leaves of ten randomly selected plants

grown in the net plot area were counted at physiological maturity and the mean values were

computed and used for further analysis.

Leaf length (cm):- The longest leaf of ten randomly selected plants grown in the net plot area

were measured from the attachment of stem up to the tip using ruler at physiological maturity

and the mean values were computed and used for further analysis.

19

3.4.2. Yield related parameters of onion

Bulb diameter (cm):- The widths of ten randomly selected bulbs, which were harvested from

the net plot area, was measured at the middle of the bulb-using caliper (Guesh Tekle, 2015;

Nigatu Muluneh, 2016) and the mean values were computed and used for further analysis.

Bulb weight (g):- The weights of ten randomly selected bulbs which were harvested from the

net plot area were measured using sensitive balance and the mean bulb weight was computed

and used for further analysis (Guesh Tekle, 2015; Nigatu Muluneh, 2016)..

Bulb size distribution: Onion bulbs are categorized based on the weight as undersized bulb

(<20g), small (20 - 50 g), medium (50 – 100 g), large (100 -160 g), and oversized (> 160 g) as

described by Lemma Dessalegn and Shimeles Aklilu, (2003) and Guesh Tekle, (2015). The

weights of such bulbs, which were harvested from the net plot area, were weighed using sen-

sitive balance and expressed in tone per hectare.

Marketable bulb yield (t/ha):- Bulbs harvested from the net plot area which were free from

damages and greater than or equal to 20g in weight were considered as marketable (Morsy et

al., 2012; Guesh Tekle, 2015). The weight of such bulbs was weighed using sensitive balance

and expressed in tone per hectare.

Unmarketable bulb yield (t/ha):- Bulbs harvested from the net plot area which were thick

necked, physiological disorder, splitted, rotten, damaged, and discolored diseased and insect

attacked and under sized (<20g), were considered as unmarketable (Guesh Tekle, 2015, Dera-

jew Asres et al., 2017). ). The weight of such bulbs was weighed using sensitive balance and

expressed in tone per hectare.

Total bulb yield (t/ha):- It was obtained by summation of Marketable and unmarketable bulb

yield.

3.5. Methods of Data Analysis

The collected data were subjected to Analysis of Variance (ANOVA) using the Statistical

Analysis System (SAS) Software version (9.0). Mean separation between treatments was done

20

using Least Significance Difference at 5% and 1% probability base on the ANOVA results as

indicated by Gomez and Gomez (1984). .

3.6. Soil sampling of experimental plots

To evaluate some of the physical and chemical properties, soil samples were collected from

the experimental sites before planting using an auger at the depth of 0-20 cm. The samples

were taken randomly in a zigzag pattern from the plots and bulked. The collected soil samples

were composited and analyzed Amhara Design and Supervision Works Enterprise Soil Labor-

atory.

The laboratory analysis of the physical and chemical properties of the composite experimental

soil results revealed that the texture of the composite soil sample was clay, in its textural clas-

sification. According to Karim and Ibrahim, (2013), suitable soil range for onion is 6.2-6.8.

However, the soil pH at Koga is moderately acidic with a pH value of 5.32. Moreover, the

experimental soil also has organic matter content of 1.926%, 5.251 ppm available phospho-

rous, 18.18cmol/kg and 0.156% total nitrogen contents (Table 3.2).

According to the rating of Tekalign Tadesse (1991), the soil of the study area is low in organ-

ic carbon as well as total nitrogen. These results indicate that there is not sufficient mineral-

ized nitrogen in the native soil for uptake of the plant during growth (Murage et al., 2000).

Therefore, there was a need to apply mineral nitrogen fertilizer to grow the crop.

21

Table 3.2: Major physic-chemical properties of the experimental soil before planting

Soil parameters Values Ranks References

PH of Soil 5.32 (%) Acidic Morphy, (2007)

Organic Carbon 1.926 (%) Weakly Tekalign, (1991)

Total Nitrogen 0.156 (%) Very low Tekalign, (1991)

Available Phosphorus 5.251 (ppm) Low Olsen et al., (1965)

Exchangeable Potassium 0.89 (cmol/kg) Low Hazelton and Morphy, (2007)

Cation Exchange Capacity

(CEC) 18.18(Meq/100g soil

Moderate Hazelton and Morphy, (2007)

Soil texture

Sand 16 (%)

Clay

Hazelton and Morphy, (2007) Clay 69 (%)

Silt 15(%)

Clay+Silt 84 (%)

3.7. Economic Analysis

To determine the economic feasibility of the treatments, economic analysis in the form of par-

tial budget analysis and marginal rate of return were calculated based on the procedures de-

veloped by CIMMYT (1988). The costs of nitrogen fertilizer, seeds as well as labor for ap-

plication of fertilizer were considered as variable costs. On the otherhand, costs that were sim-

ilar for all treatments were considered as fixed costs and were not considered in the analysis

of Marginal Rate of Return as described by CIMMYT (1988).

22

Chapter 4. RESULTS AND DISCUSION

4.1. Effects of Nitrogen Fertilizer and Intra-row Spacing on Growth of Onion

4.1.1. Days to maturity

The analysis of variance revealed that the main effects of intra-row spacing and nitrogen ferti-

lizer rates as well as their interaction highly significantly (P < 0.01) influenced leaf number

per plant of onion (Appendix Table 1).

Increasing intra row spacing as well as rate of nitrogen markedly prolonged the days to ma-

turity of the onion crop (Table 4.1). In the interaction effect, the highest days to maturity (115

days) were recorded by application of highest rates of nitrogen on plant spaced at wider intra-

row spacing. On the other hand, the shortest days to maturity was recorded when onion plants

were planted at narrower intra row spacing without nitrogen application (Table 4.2).

The relatively long maturity day due to higher nitrogen rate could be associated to prolonged

canopy growth and thereby continuing photosynthesis. This indicates that the nitrogen taken

up by plant roots may be used for cell division and synthesis of carbohydrate and thus, pre-

dominantly partitioned to the vegetative sink of the plants that resulting with a luxurious foli-

age growth of plants (Marschner, 1995).

The results are consistent with the findings of Guesh Tekle, (2015) who reported that plants

grown with higher nitrogen fertilizer (123 kg ha-1 N) at higher intra row spacing (10cm) took

longer time for maturity. On the other hand, plants supplied with low rate of nitrogen and

planted at narrower intra row spacing matured earlier.

The results of the present study are also in agreement with the findings of Weldemariam Seifu

(2015) and Wondye Mengistu, (2017) who noted that application of higher nitrogen fertilizer

rate was prolonged maturity of onion plant. Similarly, In agreement with the present study,

Dargie Miretie, (2015) reported that increasing the rate of nitrogen from nil to 32 kg N ha-1

significantly extended the number of days required to reach maturity by onion plants.

23

Similar findings also reported that plants grown at widest intra row spacing took longer time

to reach maturity while those at lowest intra row spacing matured earlier (Habtamu Tegen et

al. 2016; Weldemariam Seifu et al. 2015).

4.1.2. Plant height

The analysis of variance revealed that main effects of intra-row spacing and nitrogen fertilizer

rates and their interaction effect highly significantly (P < 0.01) influenced plant height of on-

ion (Appendix Table 1).

Increasing intra row spacing as well as nitrogen generally increased height of onion plant

(Table 4.1). In the interaction effect, application of highest rate of nitrogen on plant spaced at

wider intra row spacing recorded highest plant height (60.53cm). On the other hand, plants

planted at narrower intra row spacing without nitrogen fertilizer recorded the lowest plant

height (49.4 cm) as indicated in Table (4.2). This might be due to the application of nitrogen

mainly related to the production of new shoots and improvement of vegetative growth, which

is directly related to the increase in plant height. Additionally, there is less competition for

nutrients, moisture and light among the plants to achieve the required food for their growth

due to the wider intra-row spacing.

The results are in conformity with the findings of Fikadu Negesse (2015) who stated that the

interaction effect of 150 kg ha-1 N and 20 cm spacing recorded highly significant plant height

(30.33 cm). Similar findings were reported by Aliyu U. et al. (2008) who reported that higher

plant height of onion was recorded from the interactions effect of 100 kg ha-1 combined with

20 and 25 cm intra row spacing while lower plant height of onion was recorded from the in-

teraction effect of control plants without nitrogen and narrow intra-row spacing.

The result are also concordant with the findings of Weldemariam Seifu et al. (2015) who re-

ported longest plant height of onion when onion plants supplied with the rate of 138 kg ha-1

nitrogen at wider spaced plants while shortest plant height were recorded in the control plot

at narrower intra row spacing. Consistent with the results of the present study, Demisie Rahel,

(2018) reported that as intra-row spacing increased from 7 to 13 cm, the plant height also in-

creased from 58.79 cm to 64 cm.

24

Habtamu Tegen et al. (2016) also reported that onion plants grown at the highest intra row

spacing of 10 cm recorded the highest value of (51.42 cm). On the other hand, onion plants

grown with the lowest intra row spacing of 4 cm recorded the lowest plant height with the

value of (45.35 cm).

4.1.3. Leaf number per plants

The main effect of nitrogen and intra-row plant spacing as well as their interaction effect

highly significantly (P < 0.01) influenced the onion bulb diameter (Appendix Table 1).

Increasing intra row spacing significantly increased onion leaf number per plant across the

increasing rate of the nitrogen fertilizer (Table 4.1). The maximum number of leaves per plant

(14.1 cm) was recorded with combination of wider (10cm) intra-row spacing and higher ni-

trogen fertilization (123 kg N ha-1). On the other hand, the smallest number of leaves per/

plant (4.1 cm) was recorded in response to the interaction effects of narrowest intra-row spac-

ing (4cm) as well as nil rate of nitrogen fertilizer (Table 4.2).

The application of nitrogen is may related to production of new shoots and improvement of

vegetative growth of plants, which is directly related to the increase in leaf number (Rizk,

2012 and Kokobe et al., 2013). Similarly, less competition of plants for nutrients, moisture

and light due to wider intra-row spacing may improve growth of plants.

The results of the present study are in agreement with the results of Guesh Tekle et al. (2015)

who reported highest leaf number in interaction of (123 kg ha-1 N) and widest intra-row spac-

ing (12.5 cm). According to him, the interaction of narrowest intra-row spacing (2.5 cm and 5

cm) with nil rates of the nitrogen fertilizer rates resulted lowest number of leaves per plant,

which is in conformity to the present results.

Consistent with the results of the present study, Weldemariam Seifu et al. (2015) also indicat-

ed that highest leaf number obtained from the combination of 138 kg ha-1 N and 15 cm intra-

row spacing. Rao et al. (2013) also reported that onion plants grown at higher intra row spac-

ing of (12.5 cm) interact with 75 kg ha-1 N recorded the highest leaf number per plant of on-

ion.

25

The results are in conformity with the findings of Sikder et al. (2010) and Wondye Mengistu,

(2017) who reported that wider plant spacing and application of higher rate of nitrogen rec-

orded higher number of leaves per plant.

4.1.4. Leaf Length

The analysis of variance showed that onion leaf length was highly significantly (P < 0.01) in-

fluenced by both the main and interaction effect of intra row spacing and nitrogen rate (Ap-

pendix Table 1).

Generally, widening of the intra-row spacing and increasing rate of nitrogen increased leaf

length of onion plants (Table 4.1). In the interaction effect, plants treated with nitrogen at

rates 123 kg N ha-1 and spaced at 10 cm produced longest leaves (60.9 cm). On the other

hand, plants with the lowest leaf length (49.13 cm) produced in response to the interaction

effect of narrowest intra row spacing (4 cm) and nil nitrogen rates (Table 4.2). This could be

due to the fact that, nitrogen is a constituent of many fundamental cell components and plays

a vital role in cell division and elongation in plants. Moreover, nitrogen improves the vegeta-

tive growth which lead to increasing of leaf length through the increased photosynthetic area

and thus enhanced assimilates production and partitioning to the plants.

The results are in concordant with the findings of Muluneh Bekele, (2012) and Rao et al.

(2013), who reported that higher nitrogen fertilization increased leaf length of onion. Guesh

Tekle et al. (2015) also reported that wider intra-row spacing with application of highest rate

of nitrogen significantly increased length of onion. According to Kahsay Yemane et al.

(2013), onion plants grown at 10 cm intra-row spacing recorded the highest leaf length than

plants grown at 7.5 and 5 cm intra-row spacing which also in agreement with the results of the

present study.

26

Table 4.1: Main effect of nitrogen rates and intra-row spacing on growth of onion at Koga Ir-

rigation Scheme during the (2018) irrigation season

N-rate Day to maturity Plant height Number of Leaf length

(kg/ha) (days) (cm) leaves (cm) (cm)

0 108.0b 53.03c 7.92d 53.10b

41 108.2a 54.05bc 8.64c 54.59ab

82 109.4ab 55.59ab 9.40b 55.71a

123 110.2a 56.37a 10.64a 56.10a

P-value ** ** ** **

Intra row spacing (cm)

4 107.8b 53.5b 8.23c 54.04b

7 109.0ab 54.96ab 9.15b 54.44ab

10 110.2a 55.83a 10.08a 56.13a

P-value ** ** ** **

CV (%) 1.13 2.64 5.54 2.88

SE ± 1.24 1.44 0.51 1.58

Means followed by the same letters within a column are not significantly different at (P<

0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Variation;

SE= Standard error

27

Table 4.2: Interaction effects of intra-row spacing and nitrogen fertilizer levels on Growth of

onion plants

Intra row N- rate Day to maturity Plant height Number of Leaf length

spacing (cm) (kg/ha) (days) (cm) leaves (cm) (cm)

4 0 105.0g 49.4f 4.10i 49.1f

41 106.7efg 53.57cde 7.07g 52.4ddef

82 108.3def 54.57cde 9.67de 55.0cde

123 111.0cd 56.03c 11.80bc 57.5abc

7 0 106.0fg 51.53ef 5.0hi 50.2f

41 107.0efg 53.67cde 7.86fg 52.7def

82 109.0de 55.0cd 10.77cd 55.9bcd

123 112.0bc 56.47bc 12.10b 59.9a

10 0 106.0fg 52.57def 5.57h 51.4ef

41 107.6efg 54.17cde 8.83ef 54.7cde

82 114.0ab 59.63ab 12.97ab 58.8ab

123 115.0a 60.53a 14.10a 60.9a

P-value ** ** ** **

CV (%)

1.13 2.64 5.54 2.87

SE ± 1.24 1.44 0..51 1.58

Means followed by the same letters within a column are not significantly different at

(P<0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Varia-

tion; SE= Standard error

4.2. Effects of Nitrogen Fertilizer and Intra-row Spacing on Yield Component of Onion

4.2.1. Bulb diameter

The main effects of nitrogen and intra-row plant spacing as well as their interaction effect

highly significantly (P < 0.01) influenced the onion bulb diameter (Appendix Table 2).

Increasing the rate of nitrogen as well as widening of intra row spacing consistently increased

the bulb diameter of onion (Table 4.3). Application of highest rate of nitrogen (123 kg ha-1)

on plants spaced at widest intra row spacing (10 cm) recorded the highest bulb diameter as

28

indicated in Table 4.4. On the otherhand, combination of 4cm intra row spacing and nil rate of

nitrogen produced the narrowest bulb diameter (Table 4.4).

The development of wider bulb diameter with increased intra-row spacing and rate of nitrogen

observed in the present study could be associated with the supply of enough nitrogen, which

promotes cell elongation, above ground vegetative growth and synthesis of chlorophyll due to

less competition within plants. This may be linked to more metabolic processes that increase

dry matter production and translocation to the bulbs (Guesh Tekle, 2015).

The results of the present study are in agreement with the findings of Guesh Tekle, (2015)

who reported that increasing the rate of nitrogen fertilizer consistently increased the bulb di-

ameter of onion across the increasing intra-row spacing. The author obtained widest bulb di-

ameter in response to the application of 123 kg ha-1 N on widest spaced onion plants 12.5 cm.

On the otherhand, the narrowest average bulb diameter was obtained from plants supplied

with lower rate of nitrogen and planted at narrower intra row spacing of 2.5 cm and 5cm.

Muluneh Nigatu et al. (2018) also reported that application of nitrogen fertilizer up to 136 kg

ha-1 significantly improved the weight of onion bulbs. Demisie Rahel, (2018) also recorded

highest bulb diameter (5.63 cm) when onion plants were spaced at 13 cm intra-row spacing

followed by 10 cm intra-row spacing (5.50 cm). Similar to the results of the present study,

Derajew Asres et al. (2017) also recorded the highest bulb diameter (6.69 cm) at 15 cm intra

row spacing followed by 12.5 while significantly minimum bulb diameter (5.26 cm) obtained

at closer spacing of 7.5 cm. The results are also consistent with the finding of Nigullie et al.

(2017) where wider intra row spacing recorded highest bulb diameter.

4.2.2. Bulb weight

The analysis of variance revealed that the main effects of intra-row spacing and nitrogen ferti-

lizer rates and their interaction highly significantly (P < 0.01) influenced bulb weight of onion

(Appendix Table 2).

Increasing the nitrogen rate and widening intra row spacing generally increased average bulb

weights of onion plants (Table 4.3).

29

The highest average bulb weights were recorded at treatment combination of highest rate of

nitrogen (123 kg ha-1 N and wider intra-row spacing (10cm) while the lowest average bulb

weight was recorded at treatment combination of nil rate of nitrogen rate and narrower intra-

row spacing (Table 4.4). This might be the fact that, wider spacing accommodates less num-

ber of plants, which received adequate nutrient, moisture, and light and thus helped to im-

prove the bulb weight of onion plants (Khan et al., 2002).

In agreement with the result of the present study, Guesh Tekle, (2015) reported that ample

nitrogen supply could with wider intra row spacing result higher bulb weights of onion. Ac-

cording to the finding of various researchers decreasing the intra row spacing results signifi-

cantly decrease in bulb weight of onion (Derajew Asres et al., 2017; Demisie Rahel, 2018).

The results are consistent with the finding of Gesesew Seifu et al. (2015) who reported that as

intra row spacing increased from 10 to 15 cm, the weight of onion plant increase from 41.97

to 92.2 g. Muluneh Bekele (2012) also reported that increasing the level of N from 0 to 150

kg ha-1 significantly increased bulb weight by about 17% as compared to the control treatment

(41.35 g). Similarly, increasing the rate of nitrogen increased the bulb weight of onion, which

is in line with the present study (Dorcas et al., 2012; Morsy et al., 2012).

30

Table 4.3: Main effects of intra-row spacing and nitrogen on diameter and weight of onion

bulbs

N-rate (kg/ha) Bulb diameter (cm) Bulb Weight (g)

0 5.36b 79.0c

41 5.47b 82.3bc

82 5.81ab 88.4ab

123 6.07a 88.2a

P-value ** **

Intra row spacing (cm)

4 5.31b 81.5b

7 5.74a 83.2ab

10 5.98a 87.2a

P-value ** **

CV (%) 6.43 4.15

SE ± 0.37 3.48

Means followed by the same letters within a column are not significantly different at (P<

0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Variation;

SE= Standard error

31

Table 4.4: Interaction effect of intra-row spacing and nitrogen fertilizer levels on diameter and

Weight of onion bulb

intra row N-rate Bulb diameter Bulb Weight

(cm) (kg/ha) (cm) (g)

4 0 4.15g 63.52e

41 4.97efg 77.56d

82 5.69cde 90.51ab

123 6.44abc 92.37ab

7 0 4.49g 65.44e

41 5.34def 81.13ab

82 6.05ab 91.14ab

123 7.80a 95.28a

10 0 4.67fg 73.49d

41 5.48def 86.84bc

82 6.59ab 94.48ab

123 7.20a 96.05a

P-value ** ** **

CV (%)

6.43 4.15

SE ± 0.37 3.48

Means followed by the same letters within a column are not significantly different at

(P<0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Varia-

tion; SE= Standard error

4.2.3. Bulb size distribution of onion

Under-sized bulb yield

Results from the analysis of variance revealed that the main effects of intra-row spacing and

nitrogen fertilizer rate as well as their interaction highly significantly (P < 0.01) influenced

under sized bulb yield of onion (Appendix Table .3).

Increasing the rate of nitrogen application with widening intra-row spacing markedly de-

creased the yield of under sized bulbs (Table 4.5). The maximum under sized bulb yield was

32

recorded when onion plants were fertilized with 0 kg ha-1 N followed by 41 kg ha-1 N at spac-

ing of 4 cm intra-row spacing which could be associated with stiffer competition among

plants for growth resources including nitrogen at closer plant spacing. Conversely, the treat-

ment combination of 123 kg ha-1 N with all intra-row spacing recorded minimum under-sized

bulb yield of onion (Table 4.6).

The results of the present study are in conformity with the findings of various researchers who

reported higher undersized bulb yield at highest planting density and control treatments where

no nitrogen fertilizer applied (Nasir et al., 2007; Jilani et al., 2009; Negash Aregay et al.,

(2009)

Small sized bulb yield

The main effects of intra-row spacing and nitrogen fertilizer rate and their interaction effect

highly significantly (P < 0.01) influenced the small sized bulb yield of onion bulbs (Appendix

Table 3).

The current result indicates generally small sized bulb yield decreased with increasing of both

intra row spacing and nitrogen fertilizer rates (Table 4.5). The highest small sized bulb yield

(12.79 t/ha) was recorded by the treatment combination of 0 kg ha-1 N and 4 cm intra row

spacing which was statistically similar with those yields recorded by treatment combination of

0 kg ha-1 N with 7 and 10 cm intra row spacing (Table 4.6). On the other hand, plants supplied

with higher nitrogen rate (82 kg ha-1 N and 123 kg ha-1 N) at intra-row spacing of 7 and 10 cm

were recorded lowest small sized bulb yield of onion.

The highest yield of small sized bulbs at control plants without nitrogen fertilizer could be

associated with the reduction of above growth biomasses, leaf area and leaf length, which re-

sulted small sized bulbs.

The results are concordant with the finding of Yemane Kahsay et al. (2013) who stated that as

intra row spacing increased from 5 to 10 cm, the production of small-sized bulbs was de-

creased 23.76% to 4.4%. Consistent with the result of the present study, Bosekeng (2012) re-

ported that plants that are highly populated tend to produce high yield of small bulbs, whereas

plants at low population produce larger bulbs but with low yield.

33

Similarly, Negash Aregay et al. (2009) reported that increment in rate of nitrogen application

from 0 kg ha-1 N to 138 kg ha-1 N significantly decreased the yield of small sized bulbs of on-

ion by 61.8%. Nasreen et al. (2007) also indicated that small size bulb yield reduction were in

response to increased N fertilization. The results of the present study are also supported by the

results of Dorcas et al. (2012) and Yemane Kahsay et al. (2013) who reported higher popula-

tion density increased the yield of small sized bulbs.

Medium- size bulb yield

The analysis of variance revealed that the main effects of intra-row spacing and nitrogen ferti-

lizer rates and their interaction highly significantly (P < 0.01) influenced medium-sized bulb

of onion (Appendix Table 3).

Increasing of rate of nitrogen up to 82 kg ha-1 N and intra-row spacing up to 7cm significantly

increased the production of medium sized bulb yield of onion. Moreover, medium sized bulb

yield decreased when onion plants without nitrogen at intra-row spacing of 4 cm (Table 4.5).

The treatment combination of 82 kg ha-1 N and 4 cm intra-row spacing recorded the highest

medium sized bulb yield. On the other hand, in response to nil nitrogen and plants spaced at

4cm intra-row spacing scored lowest medium sized bulb yield of onion plants (Table 4.6).

Increasing of medium sized bulb could be associated with the supply of optimum rate of ni-

trogen as well as intra-row spacing, which were optimum for growth and enhanced productiv-

ity of the crop.

The results are conformity with the the findings of Habtamu Tegen et al. (2016) who reported

that (49%) of medium sized bulbs were produced at 6 cm intra row spacing while only 32% of

medium sized bulbs were produced at 8 cm intra row spacing.

The results of the present study are in agreement with the findings of Negash Aregay et al.

(2009) and Nasreen et al. (2007) who reported that application of optimum nitrogen rate was

produced highest weights of medium sized bulb yield. Similar findings were reported by Na-

sir et al. (2007), Rumpel et al. (2000) and Stoffela, (1996) who reported that maximum

weights of medium sized bulbs were obtained at higher planting densities.

34

Large size bulb yield

The main effects of nitrogen and intra-row plant spacing as well as their interaction effect

highly significantly (P < 0.01) influenced large sized bulb yield of onion. (Appendix Table 3).

Increasing in rates of nitrogen with increasing intra row spacing significantly increased the

production of large sized bulb yield of onion. The maximum large sized bulb yield was rec-

orded in response to the application of 82 kg ha-1 N at intra-row spacing of 7 cm but the result

is statistically similar with the application of 123 kg ha-1 N intra row spacing of 4 cm. On the

other hand, onion plants without nitrogen fertilizer and 41 kg ha-1 N interact with all intra-row

spacing’s gave the minimum value of large bulb.

The development of large size bulb with increasing of both nitrogen and intra row spacing

could be associated to the availability of resource and assimilation and less stiff competition

among the onion plants (Khan et al., 2002). This may lead to increased weights of individual

bulbs shifting from small to medium and then to large bulb categories.

Similar to the present study, Negash Aregay et al. (2009) and Kokobe et al. (2013) reported

that onion bulb size increased with increasing nitrogen dose. Islam et al. (1999) also reported

large sized bulbs in response to higher rates of nitrogen at wider intra-row spacing. The re-

sults are consistent with findings of Dawar et al. (2007); Jilani et al. (2009); Yemane Kahsay

et al. (2013) and Mallor et al. (2011) where lower population densities recorded maximum

value of large size bulbs.

Over-sized bulb yield

Main effects of intra-row spacing and nitrogen fertilizer rate as well as their interaction highly

significantly (P < 0.01) influenced the over-sized distribution of onion bulbs (Appendix Table

3).

Ample availability of growth resources including wider intra row spacing may lead to high

bulb expantion and growth, leading to the production of markedly higher yield of over- sized

bulb yield of onion (Table 4.5). The highest oversized bulb yield of onion was recorded with

combinations of 123 kg ha-1 N at 10 cm intra-row spacing. On the other hand, onion plants

35

grown at rate of 41 kg ha-1 N and nil nitrogen and plants spaced at 4 cm intra-row spacing

recorded lowest oversized bulb yield.

Ample availability of growth resources including wider intra row spacing may lead to high

bulb expansion and growth, leading to the production of markedly higher yields of over-sized

bulbs. (Rumpel et al., 2000). Consistent with the results of the present study, Khan et al.

(2002), Coleo et al. (1996) and Nasir et al. (2007) reported highest proportions of over large

bulbs at lower planting densities.

Table 4.5: Main effect of intra-row spacing and nitrogen fertilizer rates on bulb-size distribu-

tion of onion

N-rate) Undersized Small sized Medium sized Large size Oversized

(kg/ha bulb (t/ha) bulb (t/ha) bulb (t/ha) bulb (t/ha) bulb (t/ha)

0 8.00a 8.19a 10.09b 4.71c 1.11c

41 7.09ab 7.78ab 12.93a 7.54b 3.02b

82 5.74bc 6.59b 14.64a 9.50a 3.38b

123 4.68c 4.87c 13.66a 8.78ab 6.03a

P-value ** ** ** ** **

Intra row spacing (cm)

4 7.88a 8.22a 12.39b 6.12b 1.09c

7 6.12b 7.17a 14.88a 8.01a 2.76b

10 5.14b 5.19b 11.21b 8.73a 6.29a

P-value ** ** ** ** **

CV (%) 17.15 14.96 10.86 13.59 14.86

SE ± 1.10 1.03 1.39 1.04 0.50

Means followed by the same letters within a column are not significantly different at

(P<0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Varia-

tion; SE= Standard error

36

Table 4.6: Interaction effect of intra-row spacing and nitrogen fertilizer levels on Bulb-size

Distribution of onion

Intra row N-rate Undersized Small sized Medium sized Large size Large size

spacing (cm) (kg/ha) bulb (t/ha) bulb (t/ha) (t/ha) bulb (t/ha) bulb (t/ha)

4 0 14.27a 12.79a 5.19h 0.00h 0.00e

41 10.27bc 9.84b 12.58de 2.67fg 0.31e

82 5.50ef 6.30cd 22.95a 13.02b 1.53cd

123 1.48gh 3.94e 18.84b 14.28a 2.53c

7 0 12.23ab 12.58a 7.52gh 0.98gh 0.12e

41 8.49cd 9.84bc 13.62cd 3.98ef 0.65de

82 3.77fg 4.78de 15.0bc 16.33a 2.11c

123 0.67h 2.75e 11.40de 12.69b 7.18b

10 0 11.70b 10.72ab 8.57fg 1.80fgh 0.42de

41 7.59de 6.82cd 14.61cd 0.67de 0.67de

82 1.27gh 3.22e 11.45def 10.15c 8.40b

123 0.00h 0.00f 10.209efg 7.38d 15.65b

P-value ** ** ** ** **

CV (%)

17.15 14.96 10.86 13.59 14.86

SE ± 1.10 1.03 1.39 1.04 0.50

Means followed by the same letters within a column are not significantly different at

(P<0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Varia-

tion; SE= Standard error

4.2.4. Marketable bulb yield

The main effects of nitrogen highly significantly (P < 0.01) and that of the intra-row spacing

significantly (P < 0.05) influenced marketable bulb yield of onion. On the other hand, the in-

teraction effect (nitrogen and intra-row spacing highly significantly (P < 0.01) influenced the

marketable bulb yield of the onion (Appendix Table 4).

37

The highest marketable bulb yield of onion was recorded at treatment combination of 82 kg

ha-1 N and 4cm intra-row spacing. On the other hand, onion plants spaced at widest intra-row

spacing without nitrogen recorded lowest marketable bulb yield of onion (Table 4.8).

The closer intra row spacing and application of optimum rate of nitrogen leads to highest

number of bulbs with marketable size. Although plant height, number of leaves per plant and

leaf length increased with increasing spacing in the present study, higher number of plants per

unit area with enough supply of nitrogen increased marketable bulb yield.

The marketable bulb yield of onion per unit area does not completely depend up on the per-

formance of individual plants but also related with the total number of plants per unit area and

yield contributing parameters (Aliyu U et al., 2008 and Latif et al., 2010).

The results of present study are consistent to the findings of Islam et al. (1999) and Naik and

Hosamani, (2003) who reported maximum bulb yield of onion at treatment combination of

narrow intra-row spacing and optimum nitrogen fertilizer level. Hailu Dinka et al. (2015) re-

ported similar observations where highest marketable yield (34.49 t/ha) recorded from the

closest intra-row spacing (5 cm).

Generally, closer intra row spacing with optimum rates of nitrogen resulted higher marketable

bulb yield compared to widest intra row spacing as indicated by various researchers, which is

associated with the number of plants per unit area (Demise Rahel, 2018; Yemane Kahsay et

al., 2013). Soleymani and Shahrajabian (2012) and Balemi et al. (2007) also reported that

plants supplied with higher rate of nitrogen fertilization (120 kg ha-1) recorded higher value of

marketable yield.

4.2.5. Unmarketable bulb yield

The analysis of variance revealed that the main effects of intra row spacing and nitrogen rate

as well as their interaction highly significantly (P < 0.01) influenced the unmarketable bulb

yield of onion (Appendix Table 4).

With the increase in the intra-row spacing and nitrogen fertilizer rate, unmarketable bulb yield

of onion decreased significantly (Table 4.7). The highest value of unmarketable bulb yield

38

was recorded in control plots at 4cm intra-row spacing followed by rate of 41 kg ha-1 N. On

the other hand, onion plants fertilized with 82 kg N ha-1 and 123 kg ha-1 N at spacing of 7 and

10 cm recorded minimum unmarketable bulb yield (Table 4.8). This might be due to more

interplant competition for nutrient, water, light and air in narrowest plant spacing, which in-

fluences the growth of onion plants (Sikder et al., 2010).

The results of the present study in agreement with the findings of Habtamu Tegene et al.

(2016) who reported highest unmarketable bulb yield of 7 t/ha at lowest intra row spacing of 4

cm. On the other hand, onion plants spaced at wider intra row spacing (10 cm) produced the

lowest unmarketable bulb yield of 2 t/ha. Likewise, Negash Aregay et al. (2009) and Jilani et

al. (2004) also reported that nil nitrogen fertilizer rates resulted in more unmarketable bulb

yield.

The results are also concordant with the finding of Derajew Asres et al. (2017) and Demisie

Rahel, (2018) who reported highest unmarketable yield (39.52 t/ha) and lowest total marketa-

ble yield from closest and widest intra-row spacing, respectively.

Similarly, in line with the present study, Yemane Kahsay et al. (2013) reported as intra-row

spacing increased from 5 to 10 cm, unmarketable bulb yield decreased from 34.49 to 28.1

t/ha. Geremew Awas et al. (2010) also reported that plant density tested at intra-row spacing

of 4 cm scored the maximum unmarketable bulb yield.

4.2.6. Total Bulb Yield

The main effects of nitrogen and intra-row spacing as well as their interaction highly signifi-

cantly (P < 0.01) influenced the total bulb yield of onion (Appendix Table 4). Total bulb yield

increased significantly in response to increasing the rate of nitrogen fertilizer application (Ta-

ble 4.7). In the interaction effect, plants supplied with 82 kg ha-1 N and planted at 4cm intra

row spacing recorded the highest total bulb yield. On the other hand, the treatment combina-

tion of 10 cm intra row spacing and nil nitrogen recorded the lowest total bulb yields (Table

4.8).

39

The higher total bulb yield in response to the treatment combination of 4cm intra row spacing

and 82 kg ha-1 N in the present study might be due to application of optimum rate of nitrogen

fertilizer required for plants per unit area as described by Latif et al. (2010). Moreover, onion

plants planted at optimum density also helps for attaining their optimum bulb size (Rumpel et

al., 2000).

These results agree with the findings of Latif et al. (2010), and Yemane Khasay et al. (2013)

who reported that the highest onion bulb yields recorded at closest spacing. Similarly, Nig-

ullie and Biawas, (2017) found the highest total bulb yield from densely populated onion

plants than sparsely planted ones. Similar to the present study, Dereje Ademe et al. (2012)

also reported the decrease in total bulb yield with increasing intra-row spacing of shallot.

Jilani et al. (2004) showed that with increase in dose of nitrogen up to 120 kg ha-1, the total

bulb yield was increased, but below this rate, the total bulb yield began to decrease.

Soleymani and Balemi et al. (2007) also observed a significant increase in total bulb yield in

response to increased application of nitrogen.

40

Table 4.7: Main effects of intra-row spacing and nitrogen fertilizer on bulb yield of onion at

Koga Irrigation Scheme during the (2018) irrigation season

N-rate Marketable Unmarketable Total bulb

(kg/ha) Yield (t/ha) yield (t/ha) yield (t/ha)

0 26.00c 3.50a 29.50c

41 30.08b 2.81b 32.89b

82 34.11a 2.17c 34.55ab

123 32.60a 1.95c 36.28a

P-value ** ** **

Intra row spacing (cm)

4 32.20a 3.55a 35.75a

7 31.05a 2.29b 33.33b

10 28.84b 1.95c 30.83c

P-value * ** **

CV (%) 6.01 15.95 5.23

SE ± 1.85 0.42 1.74

Means followed by the same letters within a column are not significantly different at (P

<0.01); *= Significance difference at (p<0.05); ** denotes Highly Significance Difference at

(P<0.01); CV = Coefficient of Variation; SE= Standard error

41

Table 4.8: Interaction effect of intra-row spacing and levels of nitrogen fertilizer on yield of

onion at Koga Irrigation Scheme during the (2018) irrigation season

Intra row N- rate Marketable Unmarketable Total bulb

spacing (cm) (kg/ha) Yield (t/ha) yield(t/ha) yield (t/ha)

4 0 17.97g 7.27a 25.24e

41 25.41ef 3.75c 29.16e

82 43.80a 1.60ed 45.4a

123 41.63b 1.57ed 43.20ab

7 0 21.20fg 5.17b 26.37e

41 24.81e 1.70d 28.51e

82 36.17bc 1.57ed 37.74b

123 34.02d 0.71ef 34.73c

10 0 21.51fg 4.20c 25.71e

41 27.40e 1.69d 29.10e

82 33.22d 1.53ed 34.78d

123 33.23d 0.52f 33.75d

P-value ** ** **

CV (%)

6.01 15.95 5.23

SE ± 1.85 0.42 1.74

Means followed by the same letters within a column are not significantly different at (P

<0.01); ** denotes Highly Significance Difference at (P<0.01); CV = Coefficient of Varia-

tion; SE= Standard error

42

4.3. Correlation Analysis of Growth and Yield Parameters as Influenced by Intra row

Spacing and Nitrogen Fertilizer

Correlation coefficients were calculated to show the relationship of different parameters of

marketable bulb yield of onion as influenced intra row spacing and nitrogen rate. According-

ly, marketable bulb yield was highly significantly and positively correlated with most of the

tested growth parameters including plant height (r=0.65**), number of leaves (r=0.79**), leaf

length (r=0.70**), days to maturity (r=0.56**). Moreover, bulb diameter (r=0.72**), bulb

weight (r=0.87**), small sized bulbs (r=0.34*), medium sized bulb (r=0.90**), large bulb size

(r=0.88**), over-sized bulb (r= 0.33*) and total yields ((r=0.99**) were significantly and posi-

tively correlated with marketable bulb yield of onion as indicated in Table 4.9. However,

marketable yield was highly significantly and negatively correlated to under-sized bulbs (r=-

0.79**) and unmarketable bulb yields (r=-0.88**).

The correlation analysis indicates that any improvement in positively correlated parameter of

onion such as leaf number, plant height, diameter and bulb weight of bulbs and medium and

large sized bulbs contribute to increment in marketable bulb yield of onion. Similarly, reduc-

ing negatively correlated parameters including under-sized bulbs and unmarketable bulb

yields increase marketable bulb yield of onion.

44

Table 4.9: Simple correlation between growth and yield components of onion as influenced by intra row spacing and rate of

nitrogen

PH LN LL DM BD BW UN SM MD LG VL MY UY TY

PH 1

LN 0.87** 1

LL 0.84** 0.92** 1

DM 0.85** 0.89** 0.887** 1

BD 0.85** 0.93** 0.87** 0.90** 1

BW 0.80** 0.92** 0.89** 0.79** 0.87** 1

UN -0.85** -0.96** -0.89** -0.88** -0.93** -0.90** 1

SM -0.62** -0.71** -0.70** -0.76** -0.72** -0.57** 0.72** 1

MD 0.36* 0.52** 0.43** 0.23 0.44** 0.66** -0.51** -0.07 1

LG 0.58** 0.76** 0.68** 0.58** 0.70** 0.81** -0.80** -0.58** 0.74** 1

VL 0.79** 0.78** 0.75** 0.85** 0.77** 0.60** -0.74** -0.77** -0.02 0.31 1

MY 0.65** 0.79** 0.70** 0.56** 0.72** 0.87** -0.79** 0.34* 0.90** 0.88** 0.33* 1

UY -0.80** -0.87** -0.79** -0.72** -0.82** -0.89** 0.86** 0.39** -0.70** -0.71** -0.57** -0.88** 1

TY 0.59** 0.75** 0.66** 0.50** 0.66** 0.83** -0.74** 0.31 0.92** 0.89** 0.26** 0.99** -0.82* 1

Where PH= Plant height, LN= Leaf number per plants LL=Leaf lengths, DM= Day to maturity, BD= Bulb diameter, BW=Bulb weight,

UN=Undersized bulb, SM=Small sized bulb , MD=Medium sized bulb, LG= Large sized bulb, VL= Oversized bulb, UY= Unmarketable

bulb yield, MY= Marketable bulb yield, TY=Total bulb yield, *= Significant at (P<5%), **= Highly significant at (P<1%)

45

4.4. Economic Analysis

According to CIMMYT (1988), the partial budget analysis includes the total variable cost and

net benefits of each treatment. To calculate the gross incomes, the marketable yields obtained

from each treatment of onion plants were downscaled by 10%. In the present study the field

price of onion bulb and nitrogen fertilizer cost were taken as 8.00 ETB birr kg-1 and 13.60

ETB birr kg-1 respectively. The results of partial budget analysis of the study are presented in

Table 4.10. Accordingly, the highest net benefit (310933.7 ETB Birr ha-1) was recorded from

plants treated with the treatment combination of 82 kg ha-1 N and 4cm intra row spacing fol-

lowed by the treatment combination of 123 kg ha-1 N and 4cm intra row spacing.

To calculate the marginal rate of return, the dominance analysis was carried out by listing the

treatments by total variable costs in increasing order. According to CIMMYT (1988), any

treatments that have net benefits less or equal to the previous treatment is dominated which

should be removed from further analysis (Table 4.11). Accordingly, all treatment combina-

tions resulted acceptable marginal rate of return (>100%), plants, which were planted at 4 cm

intra row spacing and supplied with 82kg ha-1 nitrogen recorded the highest marginal rate of

return (8469.65%) as indicated by Table 4.12.

46

Table 4.10: Economical analysis for marketable yield of onion as affected by nitrogen fertilizer rate and intra-row spacing

Treatment

combinations

Un-adj

MY (t/ha)

Adjusted

MY (t/ha)

Gross- bene-

fit(birr/ha)

Seed cost

(birr/ha)

Labor cost

(birr/ha)

Urea- cost

(birr/ha)

TV cost

(birr/ha)

Net- bene-

fit(birr/ha) Rank

4X0 17.97 16.17 129360 1500 0 0 1500 127860 12

4X41 25.41 22.87 182960 1500 249.2 1213.96 2963.16 179996.84 8

4X82 43.8 39.42 315360 1500 498.4 2427.92 4426.32 310933.68 1

4X123 41.63 37.47 299760 1500 747.6 3641.88 5889.48 293870.52 2

7X0 21.2 19.08 152640 856.8 0 0 856.8 151783.2 11

7X41 24.81 22.33 178640 856.8 249.2 1213.96 2319.96 176320.04 9

7X82 36.17 32.53 260240 856.8 498.4 2427.92 3783.12 256456.88 3

7X123 34.02 30.62 244960 856.8 747.6 3641.88 5246.28 239713.72 4

10X0 21.51 19.36 154880 600 0 0 600 154280 10

10X41 27.4 24.66 197280 600 249.2 1213.96 2063.16 195216.84 7

10X82 33.22 30.01 240080 600 498.4 2427.92 3526.32 236553.68 5

10X123 33.23 29.91 239280 600 747.6 3641.88 4989.48 234290.52 6

47

Table 4.11: Dominance analysis for marketable yield of onion as affected by nitrogen ferti-

lizer and intra-row spacing

Treatment

Combinations

Un-adj

MY (t/ha)

Adjusted

MY (t/ha)

Total variable

Cost (birr/ha)

Net –

benefit(birr/ha) Dominance

10X0 17.97 16.17 600 154280

7X0 25.41 22.87 856.8 151783.2 D

10X41 43.8 39.42 1500 127860 D

7X41 41.63 37.47 2063.16 195216.84

10X82 21.2 19.08 2319.96 176320.04 D

4X0 24.81 22.33 2963.16 179996.84 D

7X82 36.17 32.53 3526.32 236553.68

10X123 34.02 30.62 3783.12 256456.88

4X41 21.51 19.36 4426.32 310933.68

7X123 27.4 24.66 4989.48 234290.52 D

4X82 33.22 30.01 5246.28 239713.72 D

4X123 33.23 29.91 5889.48 293870.52 D

48

Table 4.12: Marginal rate of return (MRR) of marketable onion yield as affected by nitrogen

fertilizer and intra-row spacing

Intra row spacing (cm) x

rates of nitrogen (kg/ha)

Total variable cost

(birr/ha)

Net benefit

(birr/ha) MRR (%) Rank

10X0 600 154280

10X41 2063.16 195216.84 2797.838 4

10X82 3526.32 236553.68 2825.176 3

7X82 3783.12 256456.88 7750.467 2

4X82 4426.32 310933.68 8469.652 1

49

Chapter 5: CONCLUSION AND RECOMMENDATIONS

5.1. Conclusions

Determining profitable of optimum and profitable rate of nitrogen fertilizer and optimum in-

tra- row spacing of specific area are paramount important to improve the production and

productivity of vegetable crops including onion. Thus, the objective of the present study was

to identify optimum rate of nitrogen fertilizer and plant population for economical production

of onion in Mecha district of Amhara Region.

The results of the present study showed that application of nitrogen fertilizer and intra row

spacing significantly influenced almost all the growth and yield components of onion. The

interaction effect of intra row spacing and rates of nitrogen fertilizer influenced plant height,

leaf number per plant, leaf length, days to maturity, diameter and weight of onion bulbs and

their size distribution as well as marketable yield. The growth parameters as well as yield

components increased as intra row spacing extends from 4 to 10 cm. Nevertheless, the mar-

ketable and total bulb yield decreased with increased intra row spacing (10 cm).

The interaction of closest intra row spacing (4 cm) with optimum nitrogen fertilizer rate (82kg

ha-1 N) gave the highest marketable and total bulb yield with highest net benefit and marginal

rate of return (8469.652). Application of highest rate of nitrogen fertilizer (123 kg ha-1) to

plants spaced at wider intra row spacing of 10 cm recorded highest bulb weight. Likewise,

application of 82 kg ha-1 N to plants spaced at 4 cm and 7 cm intra row spacing recorded the

highest medium sized and large-sized bulb yield respectively. On the other hand, highest rate

of nitrogen fertilizer applied to plants spaced at increased intra row spacing significantly in-

creased the over- sized bulb yield.

50

5.2. Recommendations

Based on the results of the present study, application of site and plant density specific rate of

nitrogen is necessary for economic production of onion. Accordingly, application of 82kg ha-1

nitrogen fertilizer for onion plants, which were spaced at 4 cm intra row spacing is recom-

mended for economically and agronomical feasible production of onion in the study area and

similar agro-ecologies since it recorded the highest net benefit with acceptable marginal rate

of return. However, as the results are limited to one season and location, further study should

be done over multi-seasons and locations so as to improve the production and productivity of

onion in the study area.

51

REFFERENCES

Abdissa Yadeta, Tekalign Tadesse and L.M. Pant. 2011. Growth, bulb yield and quality of

onion (Allium cepa L.) as influenced by nitrogen and phosphorus fertilization on ver-

tisol I. growth attribute biomass production and bulb yield. African Journal of Agricul-

tural Research. 6: 3252-3258.

Al-Fraihat A.H. 2009. Effect of different nitrogen and Sulphur fertilizer levels on growth,

yield and quality of onion (Allium cepa L.). Jordan Journal of Agricultural Science. 5:

155-166.

Aliyu U., Dikko A.U., Magaji M.U. and Singh A. 2008. Nitrogen and intra-row spacing

effects on growth and yield of onion (Allium cepa L.). Journal of Plant Science. 3:

188-193.

Balemi T. P., Netra and Anil S. A. 2007. Response of onion (Allium cepa L.) to combined ap-

plication of biological and chemical nitrogenous fertilizers. Acta Agriculture Slo-

venica, 89: 107-114.

Bassett M. J. 1986. Breeding of vegetable crops. AVI Publishing Co. Inc. West Port. Con-

necticut. 584p.

Brewster J. L. and Butler H. A. 1999. Effects of nitrogen supply on bulb development in on-

ion (Allium cepa L.). Journal of Experimental Botany. 40:1155-1162.

Brewster J. L. 1990. Cultural systems and agronomic practices in temperate climates. Pp. 2-

30. In: Rabinowitch, H.D. and Brewster J.L. (Eds.). Onion and allied crops. Vol. 2.

Agronomy, biotic interactions, pathology, and crop protection. CRC press, Boca Ra-

ton, Florida, USA.

Brewster J.L. 1994. Onions and other vegetable Alliums. CAB, International, Wallingford,

UK. 321p.

52

Bosekeng G. 2012. Response of Onion (Allium Cepa L.) to Sowing date and plant population.

MSc. thesis. Department of Soil, Crop and Climate Sciences. Faculty of Natural and

Agricultural Sciences. University of the Free State.

Boukary H., Haougui A., Barage M., Adam T., Roumba A. and Saadou M. 2012. Evaluation

agro-morphologique des varietes et/ou ecotypes locaux d’oignon du Niger. Interna-

tional Journal of Biological Chemistry Science. 6:3098-3106.

Brady N. C. and Weil R. R. 2002. The nature and properties of soils. 13th (ed.), Pearson Edu-

cation Asia. Delhi, India. 960p.

Bungard R.A., Wingler A., Morton J.D. and Andrews M. 1999. Ammonium can stimulate ni-

trate and nitrite reductase in the absence of nitrate in Clematis vitalba. Plant Cell Envi-

ronmet. 22: 859-866.

CIMMYT (International Maize and Wheat Improvement Center). 1988. From agronomic da-

ta to farmers’ recommendations: An economic workbook, Mexico, D.F. CIMMYT. 38-

60p.

Coelo E. F. V. A. B., Souza-de M. A. F., Conceicao and V. A. B. De souza. 1996. Perfor-

mance of onion crops under three irrigation regimes and five spacing. Pesquisa –

Agropecuaria- Brasileira, 31: 585-591.

CSA (Central Statistical Agency). 2016. Area and production of major crops. Agricultural

sample survey 2015/2016, private peasant holdings, Meher season, Statistical Bulletin

584, Addis Ababa, Ethiopia.

CSSE (Crop Science Society of Ethiopia). 2006. Farmers' participatory onion seed production

in the Central Rift Valley of Ethiopia: achievement, constraints and its implication for

the national seed system. Conference summary, The Conference of the Crop Science

Society of Ethiopia, 11, Addis Ababa, Ethiopia. pp. 26-28.

Corgan J. N. M., Wall C. Cramer T., Sammis B., Lewis J. and Schroeder. 2000. Bulb onion

culture and management. Agricultural experiment station circular. 563: 1-16.

53

Currah L. and F. J. Proctor. 1990. Onion in tropical regions. Bulletin 35. National resources

Institute. Chatham, U.K. 91-93, 151p.

Dargie Mihretie. 2015. Influence of mineral nitrogen and phosphorus fertilizer rates on

growth, yield components and bulb yield of onion (allium cepa var. cepa) at kobo,

northern Ethiopia. MSc Thesis (unpublished). Haramaya University.

Dawar NM., Wazir FK., Dawar M. and Dawar SH. 2007. Effect of planting density on growth

and yield of onion varieties under climatic conditions of Peshawar. Sarhad Journal of

Agriculture. 23:911-918.

Demisie Rahel and Tolessa Khasay. 2018. Growth and bulb yield of onion (Allium cepa L.) in

response to plant density and variety in Jimma, South Western Ethiopia. Advanced

Crop Science Technology. 6: 357. doi:10.4172/2329-8863.1000357.

Dereje Ademe, Derbew Belew and Getachew Tabor. 2012. Influence of bulb topping and in-

tra row spacing on yield and quality of some shallot (Allium Cepa L. Var. Aggrega-

tum) varieties at Aneded Woreda, Western Amhara. African Journal of Plant Science.

6:190-202.

Derajew Asres. 2014. Effect of farmyard manure and intra-row spacing on yield and yield

components of Adama Red Onion (Allium cepa L.) Cultivar under irrigation in

Gewane District, Afar Region, Ethiopia. MSc. Thesis (Unpublished). Haramaya Uni-

versity.

Dorcas A.O.A., Magaji M.D., Singh A., Ibrahim R. and Siddiqu Y. 2012. Irrigation

scheduling for onion (Allium cepa L.) at various plant densities in a Semi-Arid

environment. UMT 11th International Annual Symposium on Sustainability Science

and Management, Terengganu, Malaysia.

EARO (Ethiopian Agricultural Research Organization). 2004. Directory of released crop vari-

eties and their management. Addis Ababa. Ethiopia.

Edossa Etissa .2013. (Horticulture Irrigation Agronomy and Plant Nutrition Melkassa

Ethiopian Institute of Agricultural Research) LIVES Commodity Value Chain

54

Development Inception Workshop Addis Ababa, 21–24 January, Ethiopia’s agroecol-

ogy is suitable for producing both the edible parts and seeds of temperate and ropical

vegetable crops.

EHDA (Ethiopian Horticultural Development Agency). 2011. Assessment of development

potentials and investment options in the export-oriented fruit and vegetable sector.

EIAR (Ethiopian Institute of Agricultural Research). 2012. Directory of released crop varie-

ties and their recommended cultural practices. Addis Ababa, Ethiopia.

Fekadu Negesse. 2015. Effect of spacing and nitrogen fertilizer on the yield and yield compo-

nent of shallot (Allium ascalonium L.). Journal of Biology, Agriculture and Health

care. 5: 2224-3208.

FAO (Food and Agriculture Organization). 2012. Statistical year book Food and Agriculture

Organization, Rome, Italy.

FAOSTAT (Food and Agricultural Organization of United). 2014. Food and Agriculture. Da-

ta of the United Nations Organization.

FAOSTAT (Food and Agricultural Organization of United). 2017. Nations: Economic and

social department: the Statistical division.

Gomez K.A. and A.A. Gomez .1984. Statistical Procedures for Agricultural Research. John

Willey and Sons, New York. 390 p.

Geremew Awas, Teshome Abdissa, Kahsay Tolessa and Amenti Chali. 2010. Effect of intra-

row spacing on yield of three onion (Allium cepa L.) varieties at Adami Tulu agricul-

tural research center (mid riftvalley of Ethiopia). Journal of Horticulture and Forestry.

2: 007-011.

Gesesew Seifu, Welsetsadik Kebede and Mohammed Wassu .2015. Growth parameters of

onion (Allium Cepa L. Var. Cepa) as affected by nitrogen fertilizer rates and intra-row

spacing under irrigation in gode, southeastern Ethiopia. Forestry and Fisheries, 4: 239-

245.

55

Guesh Tekle. 2015. Growth, yield, and quality of onion (Allium cepa L.) as influenced by in-

tra-row spacing and nitrogen fertilizer levels in central zone of tigray, northern Ethio-

pia. The MSc thesis, College of Agriculture and Environmental Sciences School of

Plant Sciences, Post Graduate Directorate Haramaya University.

Habtamu Tegen, Minwyelet Jemberie, Esmelealem Miretu and Alebachew Enyew. 2016.

Influences of inter and intra row spacing on yield, yield component and morphological

characteristics of onion (Allium cepa L.) at Western Amhara region. African Journal

of Agricultural Research. 11: 1797-1804.

Hailu Dinka, Aklilu Mekonnen and Mikael Yimenu. 2015. An investigation on the influence

of intra-row spacing and variety on yield and shelf life of onion. International Journal

of Agricultural Science. 5: 559-567.

Hanelt P. 1990. Taxonomy, evaluation and history. In: H.D. Robinowitch and J. L. Brewster

(eds.). Onions and Allied crops, vol.1. CRC Press, Boca Raton, Florida. pp.1-26.

Hazelton P. and Murphy B. 2007. Interpreting soil test results: second Edition. CSIRO Pub-

lishing, Melbourne, Australia.

Islam M.K., Awal M.A., Ahmed S.U. and Baten M.A. 1999. Effect of different set size,

spacing and nitrogen levels on the growth and bulb yield of onion. Pakistan Journal of

Biological Science. 2:1146.

Jilani M.S., Khan M.Q. and Rahman S. 2009. Planting densities effect on yield and yield

components of onion (Allium cepa L.). Journal of Science Agricultural Research.

47:397-404.

Jones H.A. and L.K. Mann. 1963. Onions and Their Allies: Botany, Cultivation and Utiliza-

tion. London, Leonard Hill. 320p.

Karim S.M.R. and N.R. Ibrahim. 2013. Effect of planting time, day length, soil pH and soil

moisture on onion. International Journal of Biological Pharmacia Applied Science. 2: 807-

814.

56

Khan H., Iqbal M., Ghaffoor A. and Waseem K. 2002. Effect of various plants spacing and

different nitrogen levels on the growth and yield of onion. Journal Biological Science. 2:

545–7.

Kantona R.A.L., Abbeyb, L., Hillac, R.G., Tabil, M.A. and Jane, N.D. 2003. Density affects

plant development and yield of bulb onion (Allium cepa L.) in Northern Ghana. Jour-

nal of Vegetable Crop Production. 8:15-25.

Kokobe Woldeyohannes, Derbew Belew and Adugna Debela. 2013. Effect of farmyard

manure and nitrogen fertilizer rates on growth, yields and qualities of onion

(allium cepa L.) at Jimma Zone Ethiopia. Asian Journal of Plant Sciences. 4:1682

-3974.

Kubsa A., Desalegn P. and Verschoor R. SNV. 2006. Analysis of livelihood strategies for Ar-

ba Minch, Ethiopia, Hwassa.

Latif M.A., Choudhury M.S.H., Rahim M.A., Hasan M.K. and Pal B.K. 2010. Effects of

spacing and age of seedling on the growth and yield of summer onion. Journal of.

Agroforestry and Environment. 3:129-133

Lemma Dessalegn and Herath E. 1994. Agronomic studies on allium. In: Horticulture research

and development in Ethiopia; Proceedings of the p. 139-152, 1994 (Eds.). National

Horticultural Workshop of Ethiopia, 2nd, Dec 1-3, 1992. Institute of Agricultural Re-

search, Addis Ababa, Ethiopia. Pp. 152-162.

Lemma Dessalegn and Shimeles Aklilu. 2003. Research Experiences in Onion production.

Research Report No. 55. Ethiopia Agricultural Research Organization, Addis Ababa,

Ethiopia.

Lemma Dessalegn. 2004. Onion Production Pamphlet (Amharic version). EARO, Melkasa

Research Center, Ethiopia.

Lemma Dessalegn, Shimeles Aklilu, Selamawit Ketema and Chimdo Anchela. 2006. The

Vegetable Seed Sector in Ethiopia: Status and Future Prospects. EHSS, Proceedings of

57

the Inaugural and Third National Horticultural Workshop, Ethiopia. Volume I. 103-

109.

Mahadeen A.Y. 2008. Effect of planting date and plant spacing on onion (Allium cepa L.)

yield under rain fed in Semi-Arid conditions of Jordan. Bull Faci. Agricultural. 59:

237-241.

Mallor C., Balcells M., 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 Breeding. 130:55-59.

Marschner H. 1995. Mineral nutrition of higher plants. Second edition, Academic Press,

London. pp. 285-299.

Melkamu Alemayehu, Fentahun Tesfa, Solomon Bizuayehu and Belayneh Ayele. 2015. Am-

hara Region Horticultural Development Strategy. 2015 - 2020.

MoARD (Ministry of Agriculture and Rural Development). 2009. Rural Capacity Building

project. Course for Training of trainers on improved horticultural crop technologies.

pp. 5-19.

MoARD (Ministry of Agriculture and Rural Development). 2010. Crop variety register. Min-

istry of Agriculture and Rural Development, Addis Ababa.

Mohanty A., Behera1 P. and Harichandan S. 2015. Effect of nutrient management on the

growth and productivity of onion. Agricultural. Science. Digest, 35: 241-243.

Murage E. W., Karanja N. K., Smithson P. C. and Woomer P. L. 2000. Diagnostic indicators

of soil quality in productive and non-productive smallholders’ fields of Kenya’s

Central Highlands. Agriculture, Ecosystems and Environment. 79: 1–8.

Morsy M.G., Marey R.A., Karam S.S. and Abo-Dahab A.M.A. 2012. Productivity and

storability of onion as influenced by the different levels of NPK fertilization. Journal

of Agricultural Research Kafer El-Sheikh University. 38:171-186.

58

Muhammad S. J. 2004. Studies on the management strategies for bulb and seed production of

different cultivars of onions (Allium cepa L.). A dissertation submitted to Gomal Uni-

versity, Deraismil khan and Pakistan. 449p.

Muluneh Bekele. 2012. Effects of nitrogen, phosphorus and potassium fertilization on growth,

yield, and quality and storage life of onion (allium cepa L.). M.Sc. Thesis at Jimma

University, Southwestern Ethiopia.

Muluneh Nigatu. 2015. Assessment of onion production practice and effect of NPS fertilizer

rates on yield and yield components of onion (Allium cepa L.). Under irrigation farm-

ing system in Dembiya District, Amhara Region, Ethiopia. MSc. Thesis Bahir Dar

University.

Naik B.H and Hosamani R.M. 2003. Effect of spacing and nitrogen levels on growth and

yield of Kharif onion. Karnataka. Journal of Agricultural Science. 16:98-102.

Nasreen S. M., Haque M .M. Hossain A. and Farid A. T. M. 2007. Nutrient uptake and yield

of onion as influenced by nitrogen and sulfur fertilization. Bangladesh Journal of Ag-

ricultural Research. 32: 413-420.

Nasir M.D., Faridullah K.W., Manhaj U.D. and Shah H.D. 2007. Effect of planting density on

growth and yield of onion varieties under climatic conditions of Peshawar. Sarhad

Journal of Agriculture. 23:213-298.

Negash Aregay, Mitiku Haile and Yamoah C. 2009. Growth and bulb yield response of onion

(Allium cepa L.) to nitrogen and phosphorous rates under variable irrigation regimes in

Mekelle, Northern Ethiopia. Journal of the Dry Lands. 2:110-119.

Negasi Tekeste, Nigussie Dechassa, Kebede Woldetsadik, Lemma Dessalegn and Abu hay

Takele. 2013. Characterization of soil nutrient management and post-harvest handling

practices for onion production in the central rift valley region of Ethiopia. Agriculture,

Forestry and Fisheries. 2: 184-195.

59

Nigullie R. and Biawas P. 2017. Effect of plant and row spacing on growth and yield of onion

under mokokchung district of Nagaland. International Journal of Plant Science. 12:

28-35.

Nikus Olani and Fikre Mulugeta. 2010. Onion Seed Production Techniques: A Manual for

extension agents and seed producers, FAOCDMDP, Asella, Ethiopia.

Olsen S. R. and Dean L. A. 1965. Phosphorous. In C. A. Black (Ed.). Methods of soil analy-

sis-Part 2: Chemical and microbiological properties. 9:1035–1049.

Pervez, M.A. Ayub, C.M. Alisaleem, B. Virk, N.A. and Mahmood, N. 2004. Effect of nitro-

gen levels and spacing on growth and yield of radish (Raphanus sativus L.). Interna-

tional Journal of Agriculture and Biology. 6:504-506.

Rabinwitch H. D. and Currah L. 2002. Allium crops science: recent advances. CAB Interna-

tional, UK.

Randle WM, Ketter CA (1998). Pungency assessment in onions. Proceedings of the 19 work-

shop conference of the Association for Biology Laboratory Education (ABLE). pp.

177-196. http://www.zoo.utoronto.ca/able/volumes/copyright.htm.

Rao B. N., Roy S.S., Jha A. K., Singh I. M. and Prakash N. 2013. Influence of nitrogen and

spacing on the performance of Alliuodorosum under mid-altitude foothill condition of

Manipur. Indian Journal of Hill Farming. 26:67-70.

Rizk F. A., Shaheen A.M., Abd El-Samad E. H. and Sawan O. M. 2012. Effect of different

nitrogen plus phosphorus and sulphur fertilizer levels on growth, yield and quality of

onion (AIlium cepa L.). Journal of Applied Science Research. 8: 3353-3361.

Rumpel J., Felcynski K., Stoffella P.J., Cantliffe D. J. and Donialo G. 2000. Effect of plant

density on yield and bulb size of direct sown onions. 8lh int’. Symposium on liming of

field production in vegetable crops, Bari, Italy. Acta Horticulture. 533:179-185.

Saud S., Yajun C., Razaq M., Luqman M. and Fahad S. 2013. Effect of Potash levels and row

spacing on onion yield. Journal of Biology Agriculture and Healthcare. 3: 118-126.

60

Shaheen A., Fatma M., Rizk A. and Singer SM. 2007. Growing Onion Plants without Chemi-

cal fertilization. Research Journal of Agricultural and Biological Science. 3: 95-104.

Shojaei H., Vakili S.M.A., Khodadadi M. and Mirzae Y. 2011. Effect of different N fertiliza-

tion levels and plant population on agronomic traits and decrease in bolting of au-

tumns own onion in Shahdad Region of Kerman. Iran. Plant Ecophysiology, 3:59-64.

Sikder M., Mondal F., Mohammed D., Alam M.S. and Amin M.B. 2010. Effect of spacing

and depth of planting on growth and yield of onion. Journal of Agroforestry Environ-

ment. 4:105-108.

Seleshi Bekele. 2010. Irrigation potential in Ethiopia: Constraints and opportunities for en-

hancing the system. International Water Management Institute.

Shanmugasundaram S. and Kalb T. 2001. Suggested cultural practice for onion. AVRDC

Training guide. Pp. 1-20.

Silvertooth C. J. 2001. Row spacing, plant population, and yield relationships. Internetdo

ument. http://cals.arizona.edu/crop/cotton/comments/aprill999cc.html.

Sing AK. and Sing V. 2003. Combined effect of set size and planting distance on Kharif on-

ion bulb. Indian Journal of Agricultural Research. 37:287-290.

Stoffela, P.J. 1996. Planting arrangement and density of transplants influence sweet Spanish

onion yields and bulb size. Horticultural Science. 317:1129-1130.

Sorensen J. N. and Grevsen K. 2001. Sprouting in bulb onions (Allium cepa L.) as influenced

by nitrogen and water stress. Journal of Horticultural Sciences and Biotechnology. 76 :

501-506.

Soleymani A. and Shahrajabian M. H. 2012. Effects of different levels of nitrogen on yield

and nitrate content of four spring onion genotypes. International Journal of Agricultur-

al Crop Science. 4:179-182.

61

Sukprakarn S., Juntakool S., Huang R. and Kalb T. 2005. Saving your own vegetable seeds a

guide for farmers. AVRDC publication number 05-647. AVRDC—the world vegeta-

ble center, Shanhua, Taiwan. 25 pp.

Tadesse Adgo. 2008. Farmers, evaluation and adaption of improved onion production package

in Fogera Discrit, South Gonder, Ethiopia. (Doctoral Dissertation, Haramaya Universi-

ty).

Takashi Y. and Ayumi A. 2010. Fertilizer policies, price, and application in East Africa. Na-

tional Graduate Institute for Policy Studies. 7: 22-1. Roppongi, Minato-ku, Tokyo, Ja-

pan.

Tekalign Tadesse. 1991. Soil, plant, water, fertilizer, animal manure and compost analy-

sis.WorkingDocumentNo.13Retrievedfrom https://cgspace.cgiar.org/handle/10568/44

48.

Tisdale Sintayehu, Nelson W., Beaton J. and Halvin J. 1995. Soil Fertility and Fertilizers (5th

ed.). Macmillan Publishing Co., Inc. New York, p. 109-229.

Weldemariam Seifu, Kebede Woldetsadik and Wassu Mohammed. 2015. Growth parameters

of onion (allium cepa L.) as affected by nitrogen fertilizer rates and intra-row spacing

under irrigation in Gode, Southeastern Ethiopia. Agriculture Forestry and Fisheries.

4:239-245. doi: 10.11648/j.aff.20150406.11

Wondye Mengistu. 2017. Effects of different levels of farmyard manure and NPS fertilizers

on yield and yield components of onion (allium cepa L.) in the case of Koga, and rib

irrigation schemes, northwestern Ethiopia. M.Sc. Thesis of Bahir Dar University.

Yemane Kahsay, Derbew Belew and Fetien Abay. 2013. Effect of intra-row spacing on yield

and quality of some onion varieties (Allium cepa L.) at Aksum, Northern Ethiopia. Af-

rican Journal of Plant Science. 7:613-622.

Yemane Kahsay, Fasigaw Belay and Alemat Embay. 2016. Enhancing onion production and

productivity through introduction of seed production techniques in Central zone

of Tigray Region, Ethiopia. Academic Journal of Agricultural Research. 4:188-192.

62

Zohary D. and Hopf M. 2000. Domestication of plants in the old world. 3rd ed. Oxford

University press, pp. 197-198.

APPENDICES

Appendix 1: Mean squares of analysis of variance for plant height (PH), leaf length (LL), leaf

number per plant (LN), day to maturity (DM)

63

Mean square of growth parameters

Source of Degree of Plant Number of Leaf Day to

Variation Freedom Height Leaves length maturity

Intra-row 2 16.567** 10.175** 14.503** 17.528**

N-Fertilize 3 20.238** 12.177** 16.297** 8.880**

NxIntra-row 6 38.675** 50.184** 68.215** 49.046**

Replication 3 0.184 0.381 0.081 1.194

Error 22 2.087 0.257 2.49 1.528

CV 2.64 5.54 2.89 1.13

Appendix 2: Mean squares of analysis of variance for yield and yield related traits of onion

Mean square of bulb diameter and weight

Source of Degree of Bulb Bulb

Variation Freedom Diameter Weight

Intra-row 2 1.391** 101.365**

N-Fertilize 3 0.954** 155.742**

NxIntra-row 6 4.690** 627.489**

Replication 2 0.583 11.699

Error 22 0.133 12.124

CV 6.43 4.15

Appendix 3: Mean squares of analysis of variance for marketable and unmarketable size dis-tribution of onion

Mean square of bulb size distributions

Source of Degree of Under-sized Small-sized Medium-sized Large-sized Over-sized

64

Variation Freedom Bulb Bulb Bulb Bulb bulb

Intra-row 2 23.166** 28.327** 42.45** 21.139** 84.380**

N-Fertilize 3 19.434** 19.905** 34.46** 40.132** 36.909**

NxIntra-row 6 124.953** 73.080** 101.73** 174.116** 83.197**

Replication 2 0.335 11.534 0.72 0.551 0.44

Error 22 1.198 1.052 42.69 1.075 0.253

CV 17.15 14.96 10.86 13.59 14.86

Appendix 4: Mean squares of analysis of variance for marketable bulb yield, unmarketable

bulb yield and total yield of onion

Mean square of Marketable, Unmarketable and Total bulb yields

Source of Degree of Marketable Unmarketable Total

Variation Freedom bulb yield bulb yield bulb yield

Intra-row 2 35.034* 8.250** 72.801**

N-Fertilize 3 113.045** 4.399** 75.025**

NxIntra-row 6 334.863** 18.105** 213.212**

Replication 2 2.308 0.075 1.628

Error 22 3.414 0.173 3.017

CV 6.02 15.95 5.22