INTRODUCTION
Vegetable crops are the crucial in sustaining
food security as well as economies of both developed and developing countries. There
are number of vegetable crops grown in both rain fed and irrigation in Ethiopia
(Emana et al., 2015). These crops are characterized by
high yielder per unit of land with two or more production cycle. Vegetable
crops accommodate number of crops including hot and sweet pepper, onion, tomato,
cabbage, kale, broccoli, chilli, green bean (Emana et al.,
2015;Chewaka, 2018). Production of these crops are indispensable for developing
countries in many perspectives like fast maturing and filing time of food gaps,
providing large amount of produces per unit area, and ability of cultivating
throughout the year. Besides, the diverse agro-ecologies of the country enable
production of diversified types of vegetable crops.
Among these crops,
onion is rich with assimilable iron content used to
treat anemia. It has also therapeutic value using in cold, coughs, effective in
preventive heart attack, bronchitics and influenza (Tripathi and Lawande, 2006). Besides
its food sources it serves as sources of work opportunity and income
generation. Example; in 2013 Ethiopia exported 220,213 tons of vegetables and
generated USD 438 million (Fufa, 2017).
In Ethiopia there
were more vegetable technologies introduced and produced among which tomato is
the oldest in Ethiopia. Additionally, the production area of vegetable crop is
increasing from 80 ha to 833 ha in 1980 to 1993 and from 16578.72 ha to
22035.80 ha in 2006 to 2011 with demand from time to time. From 1993 up to 2011
the tomato production area increased to 5338ha with total production of 55635
Mg (Habtamu, 2017). Despite increasing of its production area, the
productivity per unit area is very low (Nigussie et al., 2015). This made our farmers
less beneficiaries from vegetable crops. Among vegetable crops, tomato is the
chief with multi-function crop in consumption and selling.
In Ethiopia, demand
of tomato is in increasing rate which is being imbalance with its production.
For this reason, the price inflation became double fold as compared to the last
decade. Despite climatic and soil condition of Ethiopia is suitable for large
number of vegetable crops including tomato production, their productivity is
very low. Concurrently, the total production and productivity of the crop 8
ton/ha is much less than worlds production (34 ton/ha) due to lack of improved
varieties, poor production and management, insufficient educated person on the
field and severe disease and insect pest (Binalfew et al., 2016; Alemayehu
and Alemayehu, 2017).
In Jimma zone, the onion cultivation is at backyard level which
is low yielder on limited lands. In addition, for markets in Jimma zone and surrounding, found at western and
southwestern part of Ethiopia, the onion produces were transported from the rift
valley areas where availability of irrigation facility and accessibility and
closeness to agro-industry (Emana et al., 2015). On top of these, price inflation due to
market chain with consumer population size requires immediate solution. To
boost the productivity of the crop to satisfy the demand in required quantity
and quality thereby increasing income sources of smallholder farmers and
minimizing of malnutrition problem introducing of improved varieties and
evaluating thereby selecting best variety is crucial. But, the agro-ecologies
of the zone are suitable for cultivation of any types of horticultural crops
including onion. Despite suitability of soil and climate of the areas, there
were very few works done in introducing and evaluating adaptability of improved
varieties of onion. That was why this experiment was designed with the
objective to evaluate and select well adapted, high yielder onion varieties.
MATERIALS
AND METHOD
Experimental
site and duration
The trial was done at Agaro
Agricultural Research sub-center which is testing site of Jimma
agricultural Research center (JARC). The trial site is found at Southwestern
part 397 km apart from capital city of Ethiopia. The study site located at
7’’50’35- 7’’ 51’ 00’’ N of latitude and 36’’35’30’’E longitude. The mean
altitude and average annual temperature are 1650 masl
and 20.4oC respectively. The area receives average annual RF of 1616
mm (WeldeMichael et al., 2016). The experiment was done for two consecutive
cropping season of 2016/17 and 2017/18. The experiment was conducted during dry
season using supplementary irrigation. All managements like weeding, watering
and earthing-up were done properly.
Experimental
materials and design
There were four varieties including local
materials were subjected to evaluation and these varieties were Nanthus, Adama red, Bombe red and
local variety and these varieties were collected from national horticultural
research coordinating center (Melkassa Agricultural
research Center (MARC).
The experiment was conducted in randomized
completely block design (RCBD) fashion with three replications. The
experimental plot was designed in double row fashion where two rows were used
on one ridge. Total of four ridges which include eight rows were used. Spacing
of 30cm x 50 cm between rows and ridges were used respectively. Additionally,
plants were spaced by 10 cm in which 30 plants accommodated per row and
totally, 240 plants per plot were planted on total plot size of 3m x 2.70m.
Collected data
and analysis
The onion was harvested at its appropriate
maturity stage. Data was collected from the middle two ridges of four rows with
net experimental area of 3m x 1.10m= 3.3m2 which accommodated 120
plants per plot. Different yield and yield related data of onion such as:
ª
Average
stand count at harvest (SCAH): plants from which yield and related data
collected were counted from the three replications each and average of them was
considered
ª
Average leaf
length (LL): Ten representative plants were selected and leaf length were
measured in centimeter using meter tape and the mean of the leaves length was
taken
ª
Bulbs diameter
(BlDr) (cm): diameters of marketable bulbs also from
these representative trees was taken using caliper and the average diameter was
used
ª
marketable
bulbs weight (BlWt): The weight of marketable bulbs
per plot was taken in kilogram and converted to tons per hectare
ª
Number and
weight of unmarketable bulbs: Under sized and useless bulbils per plot from
each replica were counted and weighted. The average of the three replicas was
converted to quantal per hectare, where 10Qt is
equals to 1 ton. These collected data were subjected to statistical analysis
software (SAS) vers. 9.0. The mean separation of the
varieties was done with least significant differences (LSD).
RESULTS
AND DISCUSSION
In the first cropping season, significant
variations were observed among varieties in all attributed parameters i.e average stand count at harvest per plot, average leaf
length of selected plants, average bulbs diameter, average marketable yield
number , average unmarketable yield numbers and average unmarketable yield
weight and marketable yield weight. This result was disagreed with the result
of Misgana and Awoke (2017) who suggested that non-significant
variation observed among onion varieties tested at South Omo
zone SNNPR Ethiopia. Similarly, in the second harvesting season highly
significant variation among varieties detected except stand count at harvest
and bulb diameter.
Stand
count at harvest (SCAH) and Bulb size /diameter
In the first cropping year, the result
revealed that there were significant differences among varieties based on stand
count at harvest. Accordingly, the maximum numbers of onion plants observed per
plot were 115.67 with variety Nanthus followed by
local and Adama red with the average numbers stand
count at harvest of 89.33 and 88 respectively. The minimum numbers of plants
per plot were recorded with variety Bombe red (75.67).
As far as bulbs size
concerned in the first cropping cycle, significant variations were observed
among treatments where the largest bulbs size were recorded from Adama red (6.20 cm) and Nanthus (6.13
cm) varieties which were statistically similar followed by Bombe red (5.84cm)
and local (5.15cm) varieties. Bulbs size is determined by spacing used and
number of population per unit area. The narrow the spacing or the larger the
numbers of plants per plot, the smaller the bulb size and vice versa to some
extent (Guesh, 2015).
Marketable
bulb numbers and weight per plot
Regarding marketable bulb numbers, in the
first cropping season there were variation among varieties in which the large
number of marketable bulbs recorded from Bombe red (55.67) followed by Nanthus (53.67) varieties and the least 39 bulbs number
from Adama red. In this cropping season, there was no
statistical difference observed in marketable yield weight among treatments. However,
the maximum marketable fruit weight was recorded from Bombe red (64.35 t/ha) followed
by Nanthus with the values of 50.61t/ha. But, the
least marketable yield weight was recorded with Adama
red variety 44.44 t/ha.
Regarding these
parameters in the second year, there were significant variation also observed
with Abombe red and local varieties provided largest
marketable numbers and weight with average number of bulbs 64.67 and 78.69 t/ha
and 60.33 numbers of bulbs and 81.82 t/ha respectively. The smallest numbers of
bulbs of 30.67 and 44.33 with weight of 42.12 t/ha and 24.65 t/ha were recorded
from varieties Nanthus and Adama
red respectively.
When we evaluated the onion with highly
populated per plot, the under sized unmarketable bulbs were highly recorded
whereas the lower populated provided lower unmarketable yield. Additionally,
during yield visual observation, uniform bulbs size observed from the onion
with lower population than larger population.
This agrees with the statement of Sara et al. (2015) densely populated onion plant produces smaller bulb
size and lower bulb weight.
Unmarketable
fruit number and fruit weight
In the first cropping season also, significant
variation observed with unmarketable fruit number and fruit weight where the largest
number were recorded with Adama red with average
values of 23 followed by Nanthus and Bombe red which had
statistically similar letter with the
values of 18.66 and 17.00 respectively. Similarly, the variety detected
variation statistically in unmarketable fruit weight where Adama
red gave largest unmarketable fruit weight of 4.54 Qt/ha
and the least was achieved with variety Bombe red of 1.88 Qt/ha.
This might be due to the lower population per plot enhancing marketable yield
increment.
Similarly, in stand count at harvest and leaf
length, Nanthus and Adama
red showed superior where as non-significant variation observed in marketable
bulb size. From the result also the longest average leaf length recorded from
the highly populated onion varieties i.e the highest
stand count at harvest which might be for light competition.
CONCLUSION
AND RECOMMENDATION
Based on the result, the variety with highest
stand count at harvest showed the tallest leaf length suggesting competition
for light. But, due to varietal environment preferences, yield variation
observed. Additionally, all varieties with highest number of stand count at
harvest recorded the highest number and weight of unmarketable yield.
Generally, variety Bombe red showed the greatest yield in all marketable
parameters except for number of stand count at harvest and unmarketable yields
detecting adaptability to the area. So, this variety is recommended for Agaro, its surrounding and areas with similar
agro-ecologies.
ACKNOWLEDGEMENT
The authors inspired to express heartfelt
thanks to Ethiopian Institute of Agricultural Research, Jimma
Agricultural research Center for financial support and great thanks to
technical assistances of Agaro Agricultural research
sub-center for their collaboration in success of this work from the start to
end.
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