Asian Journal of Research in Crop Science

Volume 8, Issue 4, Page 109-124, 2023; Article no.AJRCS.99291

ISSN: 2581-7167

Yield and Yield Components of Onion

as Influenced by Intra-Row Spacing
and Nitrogen Fertilizer Levels in
Rift Valley, Ethiopia
Mitiku Ashenafi a* and Sintayehu Tenaye a
a
Department of Plant Science, College of Agriculture and Environmental Science,
Debre Berhan University, Ethiopia.

Authors’ contributions

This work was carried out in collaboration between both authors. Both authors read and approved the
final manuscript.

Article Information
DOI: 10.9734/AJRCS/2023/v8i4192

Open Peer Review History:

This journal follows the Advanced Open Peer Review policy. Identity of the Reviewers, Editor(s) and additional Reviewers,
peer review comments, different versions of the manuscript, comments of the editors, etc are available here:
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Received: 05/03/2023
Original Research Article Accepted: 09/05/2023
Published: 24/05/2023

ABSTRACT

Background and Objectives: Farmers currently employ nationally approved fertilizer rates and
plant spacing when growing onions, but knowledge of plant population density and fertilizer rates
that may produce the best bulb production for different cultivars and locations is limited. As a result,
gardeners frequently use nonspecific plant population densities for various cultivars, resulting in sub-
optimal bulb yields.
Materials and Methods: A field experiment was conducted in 2019 from August to December to
study the effects of intra-row plant spacing and levels of nitrogen on yield and quality of onion
(Allium cepa L.) variety Nafis under irrigation.
Results: The main effect of intra-row spacing on stand count and both nitrogen levels and intra-row
spacing on plant height and the number of leaves per plant was observed. The interaction of
nitrogen level and intra-row distance affected days to maturity, leaf length, leaf diameter, bulb
_____________________________________________________________________________________________________

*Corresponding author: E-mail: mitikuashenafi182@gmail.com;

Asian J. Res. Crop Sci., vol. 8, no. 4, pp. 109-124, 2023

 Ashenafi and Tenaye; Asian J. Res. Crop Sci., vol. 8, no. 4, pp. 109-124, 2023; Article no.AJRCS.99291

diameter, mean bulb weight, marketable and unmarketable bulb yield, and all bulb size categories.
-1
Increased intra-row spacing to 10.5 cm and N rate of 82 kg ha increased marketable and total bulb
-1
yield by approximately 3.14 and 3.21 t ha , respectively, spacing and decreased unmarketable bulb
-1
yield by 1.38 t ha .
ha-1
Conclusion: The use of 82 kg N at the intra-row spacing of 10.5 cm was optimum for bulb
-1
production of onions. 82 kg ha N at 10.5 cm intra-row spacing resulted in the highest net benefit.

Keywords: Allium cepa L.; plant population; marketable bulb; bulb size distributions.

1. INTRODUCTION commercial bulb yield occurred at a higher

planting density, but the highest proportion of
“One of the first vegetables to be domesticated, large bulbs and average bulb weight were from a
the onion dates back more than 4,000 years. lower planting density” [11].
Between Turkmenistan and Afghanistan, where
some of its cousins still grow naturally, is where it “The enhancement of onion production and
most likely originated” [1]. The alleged onion productivity can be related to different growth
ancestor most likely moved from central Asia to factors. Onion dry bulb production depends on
the Near East. After that, it was spread nutrient requirements, location of production,
throughout the Roman Empire, first to India and variety, soil type, agronomic practices, etc. Over-
Southeast Asia, then to the Mediterranean region fertilization with nitrogen or phosphorus will
[2]. Onion (Allium cepa L.) is a day-length plant. contribute to increased pest attacks and
Several onion varieties exist depending on the stimulate succulent growth, which may
latitude at which they grow. Ever since the crop predispose the plant to damage by field or
was distributed to different parts of Ethiopia, it storage pathogens” [12]. Thus, research should
has been widely cultivated as a source of be undertaken to determine specific application
income. rates for individual fields. On the other hand,
under fertilization should also be avoided lest low
“Onions are extracting nutrients, especially yield and quality of the crop are obtained.
immobile types, because of their shallow and un-
branched root systems, which means they “The use of appropriate agronomic management
require and often respond well to the addition of has an undoubted contribution to increased crop
fertilizers” [3,4]. “Optimum fertilizer application yields. One of the major problems with onion
and cultivation of suitable varieties with production is improper agronomic practices used
appropriate agronomic practices in a specific by farmers. The optimum level of any agronomic
environment are necessary for obtaining a good practice, such as plant population, planting date,
yield of onion. Nitrogen plays an important role in harvesting date, and fertilizer of the crop, varies
the optimum yield of onions and is essential to with the environment, the purpose of the crop,
increasing bulb size and yield” [5]. “Increasing and the cultivar. In Ethiopia, optimum plant
nitrogen application rates enhances plant height, spacing and nitrogen recommendations have
the number of green leaves per plant, the weight been formulated for onions, particularly, which is
of the bulb, marketable yield, and total soluble double row spacing of 10 cm between plants and
solids” [6,7]. “Plant spacing is an important factor 20 cm between rows and application of 46 kg N
-1 -1”
in determining onion yield and quality”8. “An ha and 92 kg P2O5 ha [13,14]
essential aspect of any crop production system is
the development of a crop canopy that optimizes “However, these recommendations cannot be
interception of light, photosynthesis, and directly implemented for all types of soil types
allocation of dry matter to harvestable parts. and altitudes. This means that it is very difficult to
Planting density influences the quality, texture, give general recommendations that can apply to
taste, and yield of onions” [8]. “A crop canopy is the different agroecological zones. Therefore, to
commonly managed by manipulating row optimize onion productivity in the study area, a
spacing and plant population; as plant density specific package of recommendations for
increases, yield per unit area can increase” [9]. nitrogen fertilizer and plant spacing is required”
“Yield responses to plant population need to be [13, 15].
known, as planting density is a major
management variable used in matching crop “In Awash Melkassa District, Oromiya Region's
requirements to resources” [10]. “High Central Rift Valley, onion is one of the most

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important vegetable crops grown primarily under extending from March to April and a long rainy
irrigated conditions. There are many production season from July to September. The short rainy
constraints resulting in low yield per unit area in season is highly variable and undependable for
the districts. In the study district, growers use economic farming. Mean monthly maximum and
o
different levels of inorganic fertilizers for the minimum temperatures range from 30.9 C (May)
o o
production of different vegetables under to 26.2 C (August) and from 16.2 C (June) to
o
irrigation, particularly onion production (personal 10.8 C (December), respectively. Soils of
observation). The farmers often apply 200-300 Melkassa Agricultural Research Center are
-1
kg ha of Ammonium phosphate (DAP) (18%N, classified as Haplic Andosol [16] with a
-1
20%P) and 100-200 kg ha of Urea characteristic feature of deep pumice or volcanic
(46% N)” [15]. soil type having high water retention capacity.

“However, a few farmers use higher doses of 2.2 Experimental Design and Treatment
these fertilizers, and a significant number of
farmers use small doses of N fertilizer in the form The onion variety used was ‘Nafis’ obtained from
of Urea. This shows no specific nitrogen levels Melkasa Agricultural Research Centre (MARC)
are applied by smallholder farmers in the district. and has a very firm bulb, deep red color, and
However, the blanket recommended rates of globe in shape. The leaves are light green. The
-1
fertilizers are 200 kg ha of Diammonium cultivar takes 90-100 days for bulb harvest. A
-1 -1
phosphate (DAP) and 100 kg ha of Urea [14]. factorial combination of 0, 59, 82, or 105 kg ha
Farmers in the district also grow onions using the N and intra-row spacing of 2.5, 5, 7.5, 10.5, or
double row planting method by using different 12.5 cm were used. The experiment was then
spacing methods than the nationally arranged in 4 × 5 factorial arrangements within a
recommended spacing of 20 cm x 10 cm [13] to randomized complete block design with four
improve the yield of onions”. replications.

“Onion is traditionally grown at the recommended 2.3 Experimental Management

spacing of 40 cm x 20 cm x 10 cm in Ethiopia”
[13]. “However, farmers in the study District use Following the usual tillage practice in the study
narrower intra-row spacing. Farmers’ reasons for area, the field was poled and harrowed to a fine
using narrow plant spacing are to minimize the plow before planting. Seeds were sown in a
number of oversized bulbs produced in wider nursery on a well-prepared seedbed in July.
plant spacing, to produce bulbs with higher yields When seedlings were at the 3 or 4-leaf stage or
and optimum sizes per unit area, and to make 12 to 15 cm height, seedlings were transplanted
effective use of the limited irrigable land”. [13] At manually in the experimental field in August.
present, onion growers in the area produce Each experimental plot had 4 double rows and
onions with the application of different N rates the middle 6 single rows were used for data
and intra-row spacing or by using N rates and collection. Planting was on ridges of about 25 cm
spacing that they feel are best for obtaining height with a spacing of 40 cm between water
higher yields. Therefore, the present study was furrows, 20 cm between rows on the ridge, and
initiated to determine the most suitable intra-row 18, 21, 30, 44, and 88 plants were planted per
spacing and nitrogen fertilizer rate for optimum row for 12.5, 10.5, 7.5, 5 and 2.5 cm intra-row
onion yield and quality. 2
spacing, respectively. A 2.4 × 2.2 m (5.28m ) plot
was used for each experimental unit. The blocks
2. MATERIALS AND METHODS were separated by 1 m width and the space
between each plot within a block was 0.75 m.
2.1 Description of the Experiment Site Triple superphosphates (46% P2O5) were applied
as a source of P for the control plot and
The experiment was conducted in 2019 at Awash Diammonium phosphate (DAP) (18%N,
o o
Melkassa, located at 8 24' N latitude and 39 12' 46%P2O5) was applied for the treatment plots
E longitude with an altitude of 1550 meters based on the amount of N found in it and N was
above sea level. The site is situated in the applied as Urea (46% N). The Triple Super
Central Rift Valley of the Awash River Basin Phosphate (TSP) and Diammonium phosphate
having a semi-arid climate. Long-term 1977-2006 (DAP) were applied as a single application at
mean annual rainfall was 791.7 mm with most transplanting and nitrogen was applied in two
occurring in July and August. The rainfall follows split doses of equal amounts, at 3 and 6 weeks
a bimodal pattern with a short rainy season after transplanting. Planting was at the end of

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-1
August 2019 and harvesting was at the end of CIMMYT” [21]. Gross average bulb yield (kg ha )
December 2019. When 80% of the leaves turned (Avg, average yield of each treatment). Adjusted
-1
yellow and top fall, attaining the full size of bulbs yield (kg ha ) (AjY, the average yield was
and then cured for five days [17]. adjusted downward by 10% to reflect the
difference between the experimental yield and
2.4 Soil Sampling and Analysis yield of farmers).
Soil samples were randomly collected from the 3. RESULTS AND DISCUSSION
entire experimental site before planting to make
one composite sample. Determinations of some
3.1 Selected Soil Physicochemical
selected soil physical and chemical properties
were carried out on the composite sample. The Properties of Experimental Site
soil sample was air-dried and crushed to pass Before Planting
through a 2 mm size sieve for analysis of pH,
available P, and texture; for determination of total The laboratory analysis results conducted on
nitrogen and organic carbon, it was made to pass major soil Physico-chemical characteristics of the
through a 1 mm pore size sieve. experimental site before planting is given in
(Table. 1). Results of the soil analysis before
Soil pH was measured in 1:2.5 soil-water ratios planting showed that the soil of the site is sandy
using a pH meter. The organic carbon content of clay loam in texture. According to CIMMYT [21]
the soil was determined by the [18] methods. the soil was medium in total nitrogen (0.19%).
Available P was estimated following a procedure The experimental site had high available
of [19]. Total nitrogen was estimated by the phosphorus (18.02 ppm) and low organic matter
Kjeldahl method [20]. The results of the soil (2.15%) content according to Walkley and Black
analysis were used as inputs in determining the [21]. The pH of the soil was analysed to be 7.75
amount of nitrogen fertilizer applied. showings a nearly neutral nature of the soil. FAO
[22] reported that the preferable pH ranges for
2.5 Data Collection most crops and productive soils are 4 to 8. Thus,
the pH of the experimental soil was within the
Data on crop phenology, growth parameters, range for productive soils.
yield component, and yield were recorded
starting at transplanting to physiological maturity, Table 1. Physico-chemical characteristics of
full plant development, and harvesting time, the experimental soil before planting
respectively. The collected data were expressed
as an average based on randomly taken plants in Soil Properties Values Remark
each experimental plot. Particle size
distribution (%)
2.6 Data Analysis Clay (%) 22.08
Silt (%) 24.78
The data were subjected to analysis of variance
Sand (%) 52.13
(ANOVA) using SAS version 9.2 computer
Soil textural class Sandy clay
software (SAS Institute Inc., 2008). The least
loam
significant difference (LSD) at a 5% level of
probability was used to evaluate significant pH 7.75 nearly neutral
differences between treatment means. Organic matter (%) 2.15 low
Available phosphorus 18.02 high
-1
2.7 Economic Analysis (mg kg )
Total nitrogen (%) 0.19 medium
“Partial budget analysis was employed for
economic analysis of fertilizer application and 3.2 Phenology and Growth Parameters
plant spacing which was carried out for combined
bulb yield. The potential response of crops 3.2.1 Days to physiological maturity
towards added fertilizer and plant spacing was
estimated where the price of fertilizers and other This study showed that day to physiological
costs during planting ultimately determined the maturity of onion was significantly affected by the
economic feasibility of fertilizer application and interaction of N application and intra-row spacing
plant spacing. The economic analysis was (P<0.05), the individual treatment effects were
computed using the procedure described by also significantly different (p<0.01) (Table. 2).

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Increasing intra-row spacing and levels of the lowest plant height (47.40 cm) was obtained
applied N fertilizer delayed days of physiological in the closest spacing of 2.5 cm (Table 4). The
maturity of the crop. Statistically, the highest reduction in plant height at higher plant density
days to maturity (116.33) was recorded from a might be attributed to the possible competition for
treatment combination of 12.5cm intra-row soil moisture, light, and nutrients. This result was
spacing with 105 kg ha-1N fertilizer rate but was in line with that of Bodnar et al. [27], Karaye and
not significantly different from the combination of Yakubu [28], and Jilani et al. [29], who reported
5-12.5 spacing and 59-105 Nitrogen that the maximum height (55.48 cm) of onion
combination. Whereas, the shortest days to was recorded in the plants spaced at 25 cm,
maturity (102.66) were recorded from 2.5cm followed by 20 and 15 cm spacing which
intra-row spacing and 0 kg ha-1 nitrogen fertilizer produced 52.45 and 51.24 cm long plants,
rate. The delay in maturity due to N fertilizer respectively, whereas the least plant height
application and wider intra-row spacing could be (49.14 cm) was reported in the closet plant
possible because plants with wider intra-row spacing of 10 cm. Similarly, Lencha & Buke [30]
spacing and higher nitrogen rates did not also reported that due to high competition among
compete for resources (nutrients, sunlight, water, the closest plant spacing, onions produced the
and space) so they prolonged their vegetative least responsible for plant height. This result was
stage. This result was in agreement with the also in agreement with the previous findings of
findings of Sorensen and Khokhar [23], who Shiberu [31], who also reported that wider plant
reported that too much N can result in excessive spacing (20 cmx10 cm) produced a higher plant
vegetative growth and delayed maturity of size in onions.
onions. The results on physiological maturity
obtained from this study agreed with the fact that 3.2.3 Leaf length (cm)
an abundant supply of nitrogen delayed
physiological maturity by promoting vigorous The different intra-row spacings and nitrogen
vegetative growth of the plant [24]. fertilizer rates gave a significant variation
(P<0.01) in the leaf length (cm) and their
3.2.2 Plant height (cm) interaction was significantly different (P<0.05)
(Table 2).
This study showed that the plant height of onion -1
was significantly affected by intra-row spacing Nitrogen Fertilizer rate (82 kg ha ) gave the
and nitrogen levels (P<0.01) but their interaction highest leaf length (55.24 cm) at 10.5cm spacing
effect was not significant (Table 3). The plant and was not significantly different with the
height of the onion increased with an increase in highest rates both at 10.5 and 12.5 plant
-1 spacing. While plots with 2.5 cm spacing and no
the N rate. Plants treated with 82 kg ha N had
the tallest plants 54.33 cm from those plants N fertilizer produced the shortest leaves (38.38
-1 cm). The increase in N concentration might due
treated with 105 kg N ha .
to the availability of the nutrient for enzymes and
The control plot treated with zero N (46.03cm) proteins synthesis and less competition for
and 59 N produced significantly the lowest nutrients and moisture at wider intra-row spacing
height. Increased nitrogen levels may have due to lower plant density. Similar results were
caused plants to grow taller since nitrogen is a reported by Shiberu [31], were wider spacing
crucial component of protein, the basic building produced higher leaf lengths in various onion
block of cells, a component of all enzymes, and cultivars. Jilani et al. [29], also reported that
is also involved in metabolic processes maximum leaf length (43.68 cm) was recorded in
throughout the entire plant. Because of the plants spaced 20 cm apart, and 25 cm, (43.14
additional N fertilizer, the plants grow very well cm) though statistically not significantly different.
during the vegetative phase. In support of this, Whereas plants grown on plots with smaller
Blandino [25] and Bryla & Machado [26] spacing (2.5 cm) and no N had leaves with the
indicated that plant vigor generally increases with shortest length (38.38 cm). Similarly, Abdissa et
the supply of nitrogen fertilizer. al [32], described that N is the major constituent
of proteins and the presence of abundant protein
In this study, intra-row spacing significantly tends to increase the size of the leaves, and
increased the plant height. The plant height of accordingly, bring about an increase in
the onion increased with an increase in intra-row carbohydrate synthesis. A similar result was also
spacing. The highest height of 53.05 cm was reported by Jilani et al. [29], who found that N at
recorded in the plants spaced at 10.5 cm, -1
the rate of 200 kg ha enhanced the length of
followed by 7.5cm apart with (51.43). Whereas onion leaves.

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Table 2. Interaction effects of nitrogen rates and intra-row spacing on days to 75%
physiological maturity, leaf length (cm), and leaf diameter (cm) of Nafis onion variety grown
at Awash Melkassa
-1
N(kg ha ) Intra-rows spacing(cm) D75%PM LL(cm) LD(cm)
0 2.5 102.66e 38.38k 0.467j
5 102.667e 43.33ij 0.597gh
7.5 104.667de 41.63j 0.606gh
10.5 106.33cde 44.75i 0.641fg
12.5 107.667cde 45.10hi 0.683ef
59 2.5 104.667ed 42.89ij 0..517i
5 109.667abcd 47.70fg 0.571h
7.5 111.000abcd 51.78bc 0.66ef
10.5 112.333abc 47.79fg 0.704e
12.5 112.667abc 50.84bcd 0.693e
82 2.5 108.667bcde 48.38efg 0.803cd
5 112.667abc 48.83defg 0.799cd
7.5 113.000abc 50.18cde 0.785d
10.5 113.000ab 55.24a 0.985a
12.5 113.667ab 54.72a 0.834c
105 2.5 108.000bcde 47.15gh 0.793cd
5 113.00abc 48.42efg 0.793cd
7.5 113.667ab 49.65cdef 0.788d
10.5 114.00ab 52.97ab 0.921b
12.5 116.333a 54.81a 0.932b
LSD(0.05) 12.14 2.37 0.012
CV (%) 1.05 3.01 3.77
Where means within a column followed by the same letter(s) are not significantly different; CV: Coefficient of
variation; LSD: Least Significant Difference; DPM=Days to 75% physiological maturity; LL= Leaf length; LD= Leaf
Diameter

Table 3. The main effect of nitrogen rates and 3.2.4 Leaf diameter (cm)
intra-row spacing on plant height (cm) and
leaf number per plant of Nafis onion variety The effect of intra-row spacing, N fertilizer rate,
grown at awash melkassa and their interaction on leaf diameter (cm)
showed a significant (P<0.01) effect (Table 2).
Nitrogen level PH (cm) LNPP Significantly the highest leaf diameter (0.98 cm)
(kg ha-1) was produced by the treatment combination of
. -1
0 46.03b 9.18c 10.5 cm intra-row spacing with kg ha N fertilizer
rate. Whereas the lowest leaf diameter (0.46 cm)
59 47.00b 9.71b
was recorded from 2.5 cm intra-row spacing
82 54.33a 10.26a
without nitrogen fertilizer.
105 52.79a 10.09a
LSD (0.05) 4.79 0.35 The effect of N rates and intra-row spacing on
Intra-row -1
leaf diameter increased up to 82 kg ha and
spacing(cm) 10.5cm, respectively. This could be partly
2.5 47.40b 8.93d because wider-spaced plants with good N
5 49.13b 9.48c fertilizer application have luxurious utilization of
7.5 51.43a 9.93b nitrogen that resulted in wider leaves than plants
10.5 53.05a 10.28ab spaced at closer spacing. The increase in the
12.5 49.19b 10.43a vegetative growth of the onion plants could be
LSD (0.05) 1.98 0.39 due to the effect of N in the synthesis of the
different components of protein through the
CV (%) 47.46b 4.78
increased production of carbohydrates in the
Where means within a column followed by the same
letter(s) are not significantly different; CV: Coefficient plant system. This result was in agreement with
of variation; LSD: Least Significant Difference; that of Kahsay et al [33], who reported that the
PH=plant height; LNPP=leaf number per plant leaf diameter of different Allium species grown at

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-1
20 cm spacing was larger than plants grown at followed by 105 kg ha with (10.08) and the
15 cm which in turn was larger than plants grown lowest (9.18) number of leaves per plant was
-1
at 10 cm spacing. This result was in line with that recorded at 0 kg ha N rate. However, the
of Diriba-Shiferaw et al [34], also who concluded difference in the number of leaves per plant
-1
that increasing the application rate of N between N rates of 105 and 82 kg ha was not
increased the growth parameters of the onion significant. Even though, further increasing the N
-1
plant. fertilizer level beyond 82 kg ha did not respond
to the number of the leaf of onion per plant
3.2.5 Leaf number per plant generally, increasing application rates of N
fertilizer increase the number of leaves per plant.
The number of leaves per plant was found to be This could be attributed to the increase in the
significantly (P< 0.01) affected due to different vegetative growth of the onion plants through the
rates of applied N fertilizers and intra-row effect of N in the synthesis of the different
spacing but their interaction was not significant components of protein through increased
(Table 3). production of carbohydrates in the plant system.
Messele [5] found that the number of leaves per
The highest number of leaves per plant (10.43) plant was the highest with the application of 150
-1
was recorded at 12.5cm intra-row spacing kg ha N. A similar result was also reported by
followed by 10.5cm with (10.28) and the lowest Geries & Elsadany [6], who found that application
-1
(8.92) number of leaves per plant was recorded of 120 kg ha N significantly increased the
at 2.5cm. However, the difference in the number number of leaves of onion per plant and a further
-1
of leaves per plant between the intra-row spacing increase in the level of N (160 kg ha ) tended to
of 10.5 and 12.5 cm was not statistically decrease it. In contrast, Yeshi [38], found non-
significant. It is apparent that when intra-row significant variation in the leaf number of shallots
spacing increases, the number of plants per unit due to N application.
area becomes less; more mineral nutrients, light,
moisture, and space become available for the 3.3 Yield and Yield-Related Traits of
plant. On the other hand, it is possible that an Onion
increase in planting density resulted in a
reduction in the number of leaves because of a 3.3.1 Average bulb weight (g)
shortage of mineral nutrients, light, moisture, and
space. Many investigations also revealed that Mean bulb weight was significantly (P<0.01)
increased plant spacing increased the number of affected by intra-row spacing and nitrogen
leaves per plant on different crops. For instance, fertilizer levels and significantly (P<0.05) affected
Lencha & Buke [35], and Teshale, & Tekeste by the interaction effect. (Table 4). Statistically,
[36], reported that an increase in the planting the highest bulb weight (136.54 g and 131.17g)
density of onions resulted in a reduction in the was recorded from a nitrogen fertilizer rate of 105
number of leaves. Jilani et al. [29], also reported -1
kg ha at the spacing of 12.5 cm and a nitrogen
that the maximum number of leaves per bulb -1
fertilizer rate of 105 kg ha at the spacing of
(9.94) was obtained from the spacing of 25 cm 10.5 cm, respectively. While the lowest bulb
followed by 20 cm and 15 cm spacing, which weight of 37.93 g was obtained from a rate of 0
produced 9.58 and 9.22 leaves per plant, -1
kg ha nitrogen at the closest intra-row spacing
respectively. Whereas the closest (10 cm) of 2.5 cm.
spaced plants gave the minimum number of
leaves per plant (8.45). It might be due to the “The increment in bulb weight due to the
competition among the plants to achieve the increase in intra-row spacing by nitrogen levels
required resources for their growth due to the might be due to the growth of taller plants with a
closer spacing. Similar results were reported by higher number of leaves causing higher
Imran et al [37], on potato spacing trials which synthesis and transportation of photosynthetic
showed that plant population significantly product from source to sinks and plants widely
affected leaf number where the lowest plant spaced experienced little or no competition for
population produced significantly the highest leaf limited growth resources compared to closely
number. spaced plants” [30,39]. The increase in bulb
weight could be attributed to the increase in plant
Concerning the effect of the applied rate of N height, the number of leaves produced, and leaf
fertilizer, the highest number of leaves per plant length in response to the N treatments with less
-1
(10.26) was obtained at the rate of 82 kg ha plant nutrient competition that might have

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increased dry matter production. Tekeste et (2.37cm) was obtained from a treatment
-1
al.[40], found that application of 120 kg ha N combination of 2.5cm intra-row spacing with no
gave the best onion bulb yield. Kahsay et al [33], nitrogen. The increase in bulb diameter at wider
also reported that plants 9 cm spaced gave the intra-row spacing and the highest rate of N
lowest average weight (37.17gm) of onion bulbs fertilizer could be attributed to the availability of
while in 15cm spacing plans the average weight more nutrients and moisture due to fewer
of the bulb remained maximum (62.27gm) and competition effects and the activities of N in
also increased in N dose resulted in the different physiological and metabolic processes
-1
increased weight of bulb but above 100kg ha it through the increase in dry matter production.
started to decline. Belay et al [41], and Shiberu The present result was in line with that of Lencha
[31], also reported that wider plant spacing in & Buke [30] who reported that wider intra-row
onion resulted in heavier bulb weight. Jilani [29] spacing (12cm) gave a larger bulb diameter
also reported that significantly the highest bulb (5.13cm) of onion. Whereas the closest (9cm)
weight (59.82 g) was recorded in plants spaced spaced plants gave the lowest bulb diameter
at 25 cm apart, followed by 20 cm spacing (57.45 (3.80cm) [42]. Moreover, Jilani et al. [29],
g) weighed bulbs. reported a significantly higher bulb diameter of
5.69 cm in the widest (25 cm) plant spacing,
3.3.2 Bulb diameter (cm) followed by 20 cm spaced plants, producing a
5.00 cm bulb diameter, and the closest spacing
The effect of intra-row spacing, N fertilizer rate, of 10 cm gave 3.99 cm bulb diameter. Geries &
and their interaction showed a significant Elsadany [6] also reported a significant increase
(P<0.01) effect on bulb diameter (Table 4). in the diameter of bulbs due to the application of
-1
N up to 120 kg ha . Similar results were also
-1
The highest N fertilizer rate (105 kg ha ) gave a reported by Yadav et al. [43], who found that N at
-1
higher bulb diameter (5.71cm) at 12.5 cm intra- 150 kg ha enhanced the formation of the bulb
row spacing. Whereas the lowest bulb diameter with the highest diameter.

Table 4. Interaction effects of nitrogen rates and intra-row spacing on mean bulb weight (g)
and bulb diameter (cm) of Nafis onion variety grown at awash melkassa
-1
N(kg ha ) Intra-rows spacing(cm) MBW (g) BD (cm)
0 2.5 37.93j 2.38m
5 52.03hij 2.85l
7.5 44.70ij 3.77i
10.5 67.63ghij 3.77i
12.5 57.27ghij 4.03h
59 2.5 56.63ghij 3.23k
5 67.17fghi 3.22k
7.5 77.97defg 4.22g
10.5 107.23cb 4.51f
12.5 95.13cd 4.77e
82 2.5 76.60defg 3.62j
5 91.43cde 4.22g
7.5 90.37cdef 4.84e
10.5 106.67cb 5.14d
12.5 121.27ab 5.15d
105 2.5 68.30efgh 3.53j
5 65.00ghi 4.17g
7.5 96.17cd 5.31c
10.5 131.17a 5.52b
12.5 136.54a 5.71a
LSD(0.05) 23.5 0.12
CV (%) 17.29 1.76
Where means within a column followed by the same letter(s) are not significantly different; CV:
Coefficient of variation; LSD: Least Significant Difference; MBW=mean bulb weight; BD=bulb diameter

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-1 -1
3.3.3 Marketable bulb yield (t ha ) The highest unmarketable bulb yield (2.29 t ha )
was recorded at the narrowest intra-row spacing
-1
The effect of intra-row spacing, nitrogen of 2.5 cm and nitrogen rate of 0 kg ha
fertilizer levels, and their interaction showed a respectively. Whereas, the lowest unmarketable
-1
significant (P<0.01) effect on marketable bulb bulb yield (0.91 t ha ) was recorded at the intra-
-1
yield (Table 5). row spacing of 10.5 cm with 82 kg ha nitrogen
fertilizer levels. This is for the reason that close
-1 spacing and the lowest nitrogen rate resulted in
The highest marketable bulb yield (30.13 tha )
was obtained from treatment that received a the high undersize bulbs as the consequence of
-1 higher competition between plants.
nitrogen fertilizer rate of 82 kg ha N and intra-
row spacing of 10.5cm. Whereas the lowest -1
-1
marketable yield (17.73 t ha ) was obtained from Increasing the nitrogen level up to 82 kg.ha N
the combination of a nitrogen fertilizer level of 0 and intra-row spacing 10.5 significantly
-1
kg ha and at an intra-row spacing of 2.5 cm. decreased the unmarketable bulb yield, but the
Further, an increase in nitrogen rate beyond 82 further increment of nitrogen level beyond 82
-1
-1
kg ha and intra-row spacing beyond 10.5cm did kg.ha N and intra-row spacing 10.5 cm did not
not bring a significant difference in marketable statistically decrease the unmarketable bulb yield
bulb yield suggesting that nitrogen rate of 82 kg (Table 5).In agreement with this result, Tsegaye
-1
ha and intra-row spacing of 10.5 cm are et al [44], also showed the yield of unmarketable
optimum to obtain the highest marketable bulb bulbs decreased as the rate of nitrogen
-1
yield of onion at Melkassa. This may be due to increased up to 358 kg.ha N Likewise, Brewster
closer spacing giving the lowest bulb diameter [3] reported that under a sub-optimal supply of N,
which results in higher unmarketable yield and the marketable yields of onion and shallot can be
decreased marketable yield whereas, wider intra- severely reduced. The result indicates that at the
-1
row spacing gives a higher number of marketable nitrogen level of 82 kg ha and intra-row spacing
(>20g) and lower numbers of unmarketable (<20) of 10.5 cm increasing the nitrogen levels
sized bulbs on these treats. It is possible to affect increases the yield of marketable bulbs at the
bulb size by adjusting plant population and N expense of the unmarketable bulb yield. This
fertilizer rate that resulted in a decrease in finding was in agreement with a similar study by
undersize (unmarketable bulb yield) that leads to Demisie & Tolessa [45], who concluded that
a lack of demand on the market for the desirable plant density, has an impact on marketable bulb
bulb and increasing small, medium, large, and size.
oversize (marketable bulb yield) that lead to -1
satisfying consumer demand. Thus, based on 3.3.5 Total bulb yield (t ha )
market and consumer demand, it is possible to
The effects of both intra-row spacing and
produce onion bulbs of different sizes through
nitrogen fertilizer levels and their interaction
the selection of appropriate intra-row-spacing
effect were significant (P<0.01) on total bulb yield
and N fertilizer rates. The result of Tsegaye et al.
(Table 5). Significantly the highest total bulb yield
[44], also showed that the marketable yield of -1
(31.04 t ha ) was recorded at intra-row spacing
onion increased with an increase in nitrogen
and nitrogen level combination of 10.5 cm with
levels while the yield of unmarketable bulbs was -1
82 kg ha . Whereas, the lowest total bulb yield
significantly decreased as the rate of N increased -1
. -1 (19.06 t ha ) was recorded at the intra-row
up to 358 kg ha N and hence high rates of -1
spacing of 2.5 cm with 0 kg ha N fertilizer levels.
fertilizer N were required to maximize marketable
yield. Additionally, the findings are in line with This might be due to higher plant competition on
those of Ghaffoor et al. [3], who found that the growth resources at closer spacing, small-sized
-1
maximum nitrogen application (150 kg ha ) bulbs but large in number at much-closed plant
results in the maximum onion bulb yield spacing gives low total bulb yield, and also at
(13.20 t/ha). wider spacing beyond 10.5cm intra row spacing
-1 the number of plants per hectare reduced, thus
3.3.4 Unmarketable bulb yield (t ha ) causing a reduction in yield. From this
association, since a further increase in N rate
The effects of both intra-row spacing and -1
beyond 82 kg ha and intra-row spacing beyond
nitrogen fertilizer levels and their interaction 10.5cm did not bring a significant effect, a
effect were significant (P<0.01) on unmarketable marginal increase of N and intra-row spacing up
bulb yield (Table 5). -1
to 82 kg ha and 10.5cm, were found to be

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optimum for maximizing the total bulb yields of 0g), and oversized (>160g) to see how far the tre
onion at Melkassa. The difference in total yield atments influenced the performance of the dry
as a result of decreased population densities was bulb.
observed to be compensated in part by an
increase in yield of medium and large-sized 3.3.6.1 Small-size bulb yield (20-50g)
bulbs and a decrease in small-sized ones. A
similar result was also reported by Khokhar [46], The effect of intra-row spacing, nitrogen levels,
-1
who found that application of 60 kg ha N gave and their interaction on small-size bulb yield (t
-1
the highest bulb yield of onion ha ) showed a significant (P<0.01) difference
(Table 6).
Tegen et al [47] and Arundale et al [48] reported
similar results by stating the total yield of ripe The highest yield of small bulb size (10.29 t ha )
-1

bulbs increased with the increasing number of was observed for the treatment combination of 5
plants per square meter until an optimum was -1
cm intra-row spacing with 59 kg N ha nitrogen
reached and thereafter the yield declined. On the treatment. While the lowest yield (3.49 t ha )
-1

contrary, Ali et al [49] reported that decreasing was recorded for the treatment combinations of
the plant spacing will ultimately increase the total 12.5 cm intra-row spacing and 105 kg. ha N.
-1

yield of onions. This positive response might be The reason for this might be that close intra-row
due to the role of N in promoting the growth of spacing and suboptimum nitrogen fertilizer rate
the onion plant. restricted bulb development due to limited growth
factors that resulted in an excessive proportion of
3.3.6 Bulb Size distribution of marketable dry
small bulbs. Lencha & Buke [35] and Nourai [50]
bulbs
also reported that, as plant density increased,
The marketable dry bulb yield was grouped into s there was a progressive shift of the modal-size
mall (20 -50g), medium (50-100g), large (85 - 16 grade to smaller grades of garlic.

Table 5. Interaction effects of nitrogen rates and intra-row spacing on marketable,

-
unmarketable, and total bulb yield (t ha 1)) of Nafis onion variety grown at awash melkassa

N(kg ha-1 ) Intra-rows MB(t ha-1) UB(t ha-1) TBY (t ha-1)

spacing(cm)
0 2.5 17.73n 2.29a 19.00l
5 20.09l 1.68c 21.77k
7.5 23.04h 1.90b 24.94f
10.5 20.91k 1.51d 22.42ij
12.5 19.18m 1.28e 21.47k
59 2.5 20.83k 2.00b 22.83hi
5 22.28i 1.16e 23.44g
7.5 21.93i 2.00e 23.13gh
10.5 22.18i 1.19e 23.38g
12.5 21.32j 0.97f 22.28j
82 2.5 25.05g 1.27e 26.32e
5 27.15cd 0.94f 28.10c
7.5 27.40c 1.48d 28.88b
10.5 30.13a 0.91f 31.04a
12.5 26..41e 0.92f 27.34d
105 2.5 27.08cd 1.01f 28.09c
5 26.24e 1.19e 27.43d
7.5 26.94d 1.30e 28.24c
10.5 29.42b 1.23e 30.66a
12.5 25.71f 1.00f 26.71
LSD(0.05) 0.69 0.15 0.67
CV (%) 1.54 6.61 1.06
Where means within a column followed by the same letter(s) are not significantly different; CV: Coefficient of
variation; LSD: Least Significant Difference; MB=marketable bulb; UB=unmarketable bulb; TBY=total bulb yield

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Table 6. Interaction effects of nitrogen rates and intra-row spacing on the bulb size distribution
of marketable dry bulbs (t ha-1) of Naïfs onion variety grown at awash melkassa
-1
N(kg ha ) Intra-rows spacing(cm) US SS MS LS OS
(t ha-1) (t ha-1) (t ha-1) (t ha-1) (t ha-1)
0 2.5 2.02a 7.53cd 6.16j 3.04k 0.457m
5 1.91b 6.25g 8.31i 6.131i 1.63k
7.5 1.62c 6.84e 9.29h 7.37efg 1.80k
10.5 1.26e 7.28d 9.41gh 7.06gh 2.10j
12.5 1.13f 7.83c 6.59j 7.64e 2.20ij
59 2.5 1.38d 6.17g 7.78i 4.88j 0.63m
5 0.94g 10.29a 9.15h 6.72h 2.01j
7.5 0.90hij 8.25b 11.75de 6.23i 2.75h
10.5 0.87hijk 5.42i 10.89f 7.05gh 3.27f
12.5 0.85ijkl 4.19k 10.64f 7.12fgh 3.59e
82 2.5 1.00g 7.361d 11.63de 6.09i 0.97l
5 0.83jklm 6.50efg 11.20ef 8.75d 2.38i
7.5 0.81klm 6.68ef 11.751de 9.08cd 3.36f
10.5 0.81klmn 6.37fg 15.15a 10.81a 3.85d
12.5 0.77lmn 4.531k 12.46bc 9.57b 4.13c
105 2.5 0.92ghi 5.791h 12.56b 7.04gh 1.06l
5 0.82jklm 4.91j 12.83b 7.55ef 3.06g
7.5 0.76mn 4.33k 11.97cd 9.26cb 4.37b
10.5 0.731n 3.79l 14.80a 9.56b 4.87a
12.5 0.58o 3.49l 11.48de 9.69b 4.97a
LSD(0.05) 0.08 0.36 0.57 0.49 0.21
CV (%) 4.55 3.29 3.11 3.98 4.65
Where means within a column followed by the same letter(s) are not significantly different; CV: Coefficient of
variation; LSD: Least Significant Difference; US=under size=small size; MS=medium size; LS=large size;
OS=oversize

3.3.6.2 Medium bulb size yield (50-100g) 3.3.6.3 Large size bulb yield (100-160g)

The effect of intra-row spacing, nitrogen levels, The responses of large bulb-size yield due to the
and their interaction on medium bulb size yield different levels of nitrogen fertilizer, intra-row
(50-100g) showed a significant (P<0.01) spacing, and their interaction effects were
difference (Table 6). significant (P<0.01) (Table 6).

The highest yield of medium bulb size (15.15 t Large bulb size yield increased at wider planting
-1
ha ) was recorded for intra- row spacing of 10.5 density with optimum nitrogen level according to
-1
cm and 82 kg ha N treatment combination. these study conditions. Thus, the highest large
-1
While the lowest yield of medium bulb size (6.16 bulb size yield (10.80 t ha ) was recorded at
-1 -1
t ha ) was observed for a treatment combination 10.5 cm intra- row spacing and 82 kg. ha N
of 2.5 cm intra-row spacing and with no nitrogen combination. Whereas, the lowest yield of large
-1
application. This is probably because with the bulb size (3.03 t ha ) was observed at a high
increase in applied nitrogen and intra-row planting density of 2.5 cm intra-row spacing with
spacing the yield of medium bulb size increases no nitrogen application. However, further
due to an increase in the weight of individual increase of nitrogen fertilizer rate beyond 82 kg
-1
bulbs thus transferring the bulbs from the small ha N and intra-row spacing beyond 10.5 cm had
to the mediums. The result agreed with that of a decreasing effect on large bulb size yield. The
Lemma & Shimeles [13], who reported that reason that yields of large bulbs increased
investigation on a different level (0, 46, 92, and significantly by increasing intra-row spacing and
-1
138 kg. ha ) of N and P2O5 the difference was N rate with a corresponding decrease in the yield
observed only on different levels of N and at 92 of small bulbs was due to resource availability
-1
kg. ha N there was better vegetative growth and and less competition increased the weight of
the average bulb weight increased to 49 and 60 individual bulbs thus transferring the bulbs from
g/bulb. This is also the most proffered size in the the medium to the large grades. This result was
local and export markets. in agreement with the results of Kahsay et al.

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[33], who reported that the yield of large tubers 3.3.7.1. Undersize bulb yield (<20g)
increased significantly by the wider spacing with
a corresponding decrease in the yield of small The effect of intra-row spacing, nitrogen levels,
tubers due to reduced inter-plant competition at and their interaction on under-size bulb yield (t
-1
low plant density. Messele [5] reported that intra- ha ) showed a significant (P<0.01) difference
row spacing had a significant effect on the bulb (Table 6). The yield of a very small bulb size
weight of onion with 20 and 25cm spacing (<20g) increased at higher planting density and
recording similar bulb weight but significantly low levels of nitrogen. Thus, the highest yield of
-1
higher than 10 and 15 cm spacing. very small bulb size (2.02 t ha ) was observed at
the highest planting density of 2.5 cm intra-row
3.3.6.4 Oversized bulb yield (>160g) -1
spacing with 0 kg ha N treatment combination
-1
and the lowest yield (0. the ) was recorded at
Both the main and interaction effects of
the widest intra-row spacing of 12.5 cm with 105
nitrogen level and intra-row spacing had -1
kg ha N. High under-sized bulb yield in closed
significant (P<0.01) effects on oversized bulb
intra-row spacing and non-nitrogen fertilizer
yield (Table 6).
conditions could be due to interplant competition
for growth resources. This result was in
The results showed that increasing intra-row
agreement with other similar studies by Dawar et
spacing and nitrogen rate increased the yield of
al [52]. found in onion that the maximum
oversized bulbs. Among the 20 treatment
- (738.11g) weight of a very small bulb at the
combinations, two of them, N rate of 105 kg ha -2
1 highest planting density of 80 plants 4m was
N with 12.5 cm and 10.5 cm intra-row spacing,
noted, while the minimum (181.78g) weight of
gave the highest yield of oversized bulbs of 4.97
-1 -1 very small bulbs was achieved at planting density
t ha and 4.87 t ha respectively. On the other -2
-1 of 40 plants 4 m . In support of the present result
hand, the lowest (0.457 t ha ) yield of oversized
Netsanet [53], reported that increased N fertilizer
bulbs was recorded from a treatment -1
from 0 to 120 kg ha N increased the number and
combination of 2.5 cm intra-row spacing with 0
-1 weight of very large-sized cloves by 46.94% and
kg ha N.
51.37%, respectively compared to the control.
In this study, it was evident that the effect of 3.4 Stand Count
nitrogen and intra-row spacing was to increase
the number of bulbs that grew sufficiently to be The effect of nitrogen fertilizer and the interaction
incorporated in the larger grades. The reasons effect of nitrogen fertilizer and intra-row spacing
that the yield of an over-sized bulb increased did not show a significant effect on stand count
with wider spacing and a higher rate of nitrogen difference while there was a highly significant
might be due to decreased intra-plant (P<0.01) difference among the intra-row spacing
competition at low density or relatively more levels (Table 7).
available nitrogen or other soil nutrients and
luxurious utilization of essential resources to the Table 7. The main effect of nitrogen rates and
plant at wider spacing and high rate of nitrogen. intra-row spacing on stand count (%)of the
Similar results were reported by Belay et al. [41], Nafis onion variety grown at awash melkassa
Lencha & Buke [30], and Shiberu [31], where -1
wider plant spacing in onions, resulted in heavier Nitrogen level (kg ha ) Stand count (%)
bulb weight. This result was also in agreement 0 87.78a
with that of Israel et al [51]. who reported a 59 87.72a
significant effect of nitrogen on the number and 82 87.72a
weight of large-sized potato tubers, and also that 105 87.84a
of Yeshi et al [38]. on shallot crops that increased LSD(0.05) NS
leaf length resulted in a significant increase in Intra-row spacing(cm)
bulb size. 2.5 74.43e
5 78.51d
3.3.7 Bulb Size distribution of unmarketable 7.5 89.48c
dry bulbs 10.5 98.60a
12.5 97.81b
The unmarketable dry bulb size was also taken LSD(0.05) 0.45
as bulbs weighted less than 20 g to see how far CV (%) 0.62
the treatments influenced the performance of the
dry bulb.

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Table. 8. Economic analyses for N rates and intra-row spacing experiment of onion
-1
N(kg ha ) with Unadjusted Adjusted Gross Variable Net MRR%
intra-row(cm ) marketable marketable Benefit cost Benefit
-1 -1 -1 -1
combination yield (kg ha ) yield (kg ha ) (Birr ha ) (Birr) (Birr ha )

0*12.5 19180 17262 51786 1690.35 49926.61 0

0*10.5 20910 18819 56457 1786.98 54491.31 4294.37
0*7.5 23040 20736 62208 2815.66 59110.77 408.24
82*12.5 26410 23769 71307 4200.21 66686.77 497.43
82*10.5 30130 27117 81351 4296.84 76624.47 9349.1

The highest plant stand (98.60%) was recorded However, for resource-full farmers (investors), 82
-1
at 10.5cm intra-row spacing, while the lowest kg ha N with 10.5 cm intra-row spacing
plant stand (74.43%) was recorded at the intra- combination was also profitable with the highest
nd
row spacing of 2.5cm. This might be due to net benefit and recommended as 2 option.
intense plant competition for light, nutrients, and
soil moisture at closer plant spacing, as a result The marketable bulb yield was adjusted by a
of which the plant becomes weaker, die, and 10% adjustment coefficient and the marginal rate
higher number of losses of the onion plant. of return (MRR) and net benefits are calculated
by adding a 10% birr/kg increase from the
3.5 Cost-Benefit Analysis current fertilizer price and the field price of onion
-1
was 3.00-birr kg and the market price of Urea
-1 -1
In the result of the present study, the costs for and seed were 13.30 kg and 2.40 kg
the different Nitrogen fertilizer, seed, and labor respectively. And also labor incurred price for
-1
costs for transplanting and fertilizer application fertilizer application and planting was 77.96 qt
varied according to their purchasing and incurred and 0.0004 Birr/ seedling respectively.
cost requirements being other costs were
constant for each treatment. To recommend the 4. CONCLUSION
present result for producers, it is necessary to
estimate the minimum rate of return acceptable Understanding how intra-row spacing and
to producers in the recommendation domain. nitrogen fertilizer amounts affect onion output
Based on partial budget analysis, with a 10% and yield components is an important concern to
increase in input price and a 10% decrease in enhance its productivity.Applied N fertilizer levels
output price, the highest net benefit 76624.47.16 revealed highly significant differences in all of the
birr was obtained from a treatment combination growth, bulb characters, and yield except the
-1
of 82 kg ha N with 10.5 cm intra-row spacing stand count of onion and intra-row spacing also
with a marginal rate of return of 9349.16 % but revealed highly significant differences in all of the
the highest net benefit (54491.31 birrs) with the growth, bulb characters, and yield. It is
-1
least cost (1786.98-birr ha ) were obtained from concluded that different spacing, N rate, and their
-1
the combination of 0 kg ha N with 10.5 cm intra interaction affect the yield of onion, finally for
row spacing with (4294.37%) MRR. areas like Adaamaa district, Awash Melkassa
Kebele (East Shewa zone of the Oromiya
Only in one growing season (Table 8). This Region) intra row spacing of 10.5 cm with 82 kg
means that for every 1.00 birr invested for 82 kg -1
-1
ha N rate is highly recommended to earn
N ha application with 10.5cm intra-row spacing maximum marketable yield and to reduce
in the field, producers can expect to recover the unmarketable bulb yield, Whereas the
1.00 birr and obtain an additional 102.94 birr. combination of 2.5cm intra row spacing with 0
-1
level N rate and 12.5cm with105kgN ha found
According to CIMMYT [21] the minimum to be inferior for marketable bulb yield as
acceptable marginal rate of return (MRR %) measured by unmarketable bulb yield,
should be between 50 and 100%. The present undersized (<20g) and oversized (>160) bulb
study indicated that MRR is much greater than category. However, multi-location and multi-
100%. Therefore, the most attractive rates for season research could be suggested to reach full
small-scale farmers with low cost of production recommendation because a single experiment at
-1
and higher benefits, in this case, were 0 kg ha N one location and one season may not be
and 10.5cm intra-row spacing combination. applicable in climatic and location variability. The

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agronomic and economic feasibility study is Agricultural and Soil Science. 2016;4(1):1-
needed to know the applicability of the different 8.
spacing and N rates with other agronomic 8. Atalay D, Alemayehu M, Ayana D. Effects
management practices. of intra-row spacing and nitrogen fertilizer
rates on growth, and yield of onion (Allium
ACKNOWELEDGMENTS cepa L.) under irrigation in mecha district
of amhara, ethiopia. International Journal
Thanks go to the Melkassa Research Center of Bioorganic Chemistry, 2022;7(1):17.
staff in general, and especially to W/Ro 9. Mahil EIT, Lokanadhan S. Yield and yield
Selamawit Ketema, Ato Sulti Kedr, Shimeles components of winter cotton (Gossypium
Akelilu, Jimbicho Geleto, Damtew Aragaw, Yosef hirsutum L.) genotypes influenced by plant
Alemu, and Dame Nagewo, for their guidance spacings. International Journal of Plant &
and access to facilities whenever required. Soil Science. 2018:1-6.
10. Deressegn F, Telele T. Review on effects
COMPETING INTERESTS of inter and intra row spacing on yield and
yield components of soybean [Glycine max
Authors have declared that no competing (L.) Merrill] in Ethiopia. Journal of Biology,
interests exist. Agriculture and Healthcare. 2017;7(7):53-
59.
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