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American Journal of Bioscience and Bioengineering
2021;
9(1): 1-7
http://www.sciencepublishinggroup.com/j/bio
doi: 10.11648/j.bio.20210901.11 X
ISSN: 2328-5885 (Print); ISSN: 2328-5893 (Online)
Effects of Plant Spacing and Time of Harvesting on Yield
and Tuber Size Distribution of Potato (Solanum tuberosum
L) Variety Southeast Ethiopia
Demis Fikre Limeneh
1, *
, Fekadu Gebretensay Mengistu
2
, Gizaw Wegayehu Tilahun
1
,
Dasta Tsagaye Galalcha
1
, Awoke Ali Zeleke
1
, Nimona Fufa Hundie
1
1
Kulumsa Agricultural Research Center, Ethiopian Institute of Agricultural Research, Assela, Ethiopian
2
Debre Zeit Agricultural Research Center, Ethiopian Institute of Agricultural Research, Debre Zeit, Ethiopian
Email address:
*
Corresponding author
To cite this article:
Demis Fikre Limeneh, Fekadu Gebretensay Mengistu, Gizaw Wegayehu Tilahun, Dasta Tsagaye Galalcha, Awoke Ali Zeleke, Nimona Fufa
Hundie. Effects of Plant Spacing and Time of Harvesting on Yield and Tuber Size Distribution of Potato (Solanum tuberosum L) Variety
Southeast Ethiopia. American Journal of Bioscience and Bioengineering. Vol. 9, No. 1, 2021, pp. 1-7. doi: 10.11648/j.bio.20210901.11
Received: December 19, 2020; Accepted: January 6, 2021; Published: February 9, 2021
Abstract:
Potato is one of the most important crops in the farming system of Bekoji and Kofele in the cool highlands of Arsi
where potato is usually grown biennially during the main and ‘bulg’ seasons. ‘Belete’ has been the dominant potato variety in
these areas for the last ten years now and farmers prefer to grow this variety for its high productivity and resistance to late
blight disease. Nevertheless, farmers have complaints on its big sized tubers, considered as unmarketable, which costs them
more seed to cover a given area of land and less suitable for cooking. Besides, farmers often use random population density
and time of harvesting, which also contribute to this problem. The present study was therefore intended to manage the tubers’
size distribution of this variety without negatively affecting the yield of the crop through modifying plant spacing and time of
harvesting from previously recommended practices. Twelve combinations of four plant spacing and three time of harvesting
were studied on variety “Belete’ at Bekoji and Kofele in the main seasons of 2018 and 2019. The experiment was laid out in a
completely randomized block design with 4x3 factorial arrangement in three replications. The analysis of variance revealed
that the interaction effect of spacing and time of harvesting significantly (p<0.001) affected the marketable tuber yields. The
narrow spacing (60cmx20cm) or high population treatment (83,333 plants/ha) with 120 days after planting resulted in the
highest marketable and total tuber yield compared to the rest. While the least yields were recorded from the wider spacing of
75cmx30cm (44,444plants/ha) and early harvesting (90 days). The spacing 60cmx20cm did 17.2% increment in marketable
yield over the previously recommended spacing of potato (75cmx30cm, 44,444plants/ha). From this study, therefore, it can be
recommended for Belete that the narrow spacing of 60cmx20cm and harvesting at 120 days after planting could be the
optimum spacing and time of harvesting to produce marketable tubers.
Keywords:
Days After Planting, Tuber Size Distribution, Marketable Yield, Unmarketable Yield
1. Introduction
Potato (Solanum tuberosum L.) is one of the most
important agricultural crops in the world. In volume of
production, it ranks fourth in the world after maize, rice and
wheat, with an estimated production area of 18.9 million
hectares [1]. Potato is regarded as a high-potential food
security crop because of its ability to provide a high yield of
high-quality product per unit input with a shorter crop cycle
(mostly <120 days) than the major cereal crops [2].
The average composition of the potato tuber is about 80%
water, 2% protein and 18% starch. As a food it is one of the
cheapest and easily available sources of carbohydrates and
protein and contains appreciable amount of vitamin B and C
as well as some minerals. Moreover, protein of potato is of
high biological value [3, 4].
Global production of potatoes was 388 million tons, led by
China with 64% of the world total. China is now the biggest
2 Demis Fikre Limeneh et al.: Effects of Plant Spacing and Time of Harvesting on Yield and Tuber Size Distribution of
Potato (Solanum tuberosum L) Variety Southeast Ethiopia
potato producer, and almost a third of all potatoes are
harvested in China and India [5]. Secondary producers were
Algeria and Nigeria [5] while the current average potato
productivity in Africa has been reported to be about 13.22 t
ha
-1
which is well below the maximum productivity of 20.11
t ha
-1
[5]. The average yield of potato in Ethiopia ranges only
between 8 to 10 t ha
-1
, which is much lower than the yields
obtained in the Sudan (17 t ha
-1
) and Egypt (26 t ha
-1
) [6].
Although, the edaphic and climatic conditions are suitable for
production of high quality potato in Ethiopia, the national
average production is as low as 8 t ha
-1
[7].
In Oromia Region potato production coverage was
estimated about 38,925.67 ha from which 484,831.16 tons of
potato was produced with an average yield of 12.46 t ha
-1
[8]
.
In Ethiopia, potato is a high potential food security crop due
to its high yield potential per hectare and nutritious tubers.
Potato production in Ethiopia is possible on about 70% of the
arable land [9]. Potato is a leading vegetable crop in Ethiopia
and smallholder farmers cultivate about 50,000 ha each
season [10]. Moreover, in Ethiopia potato production serves
as a means to overcome food shortage periods ‘hungry
months’, since it matures before the harvest of other food
crops such as cereals [11].
The yield of potato is influenced by a number of factors,
which include nitrogen, cultivar, seed piece spacing, climatic
conditions and geographic location [12]. Plant spacing and
time of harvesting are amongst the factors which could affect
the yield as well as the size of tubers in potato. As plant
density increases (closer spacing) there is a marked decrease
in plant size and yield per plant, while at lower plant density
(wider spacing), the reverse could happen. This effect is due
to inter-plant competition for water, light and nutrient. It is
therefore, essential to understand how individual plants
interact with each other and the environment and to possibly
come up with the ideal crop density level to optimize yields
and tuber sizes.
In Ethiopia it is a common practice to use a spacing of
75cm (inter row) x 30cm (intra row) and/or 60cm x 20cm to
produce potato for table and seed purpose respectively for all
varieties. However, using this spacing, the commonly grown
variety ‘Belete’ produces large tubers, which are not usually
acceptable by farmers, either for seed or table purposes.
Besides, variations in tuber size distribution among varieties
influence the seed rate to be used for a given area of land.
Some varieties such as ‘Belete’ produces large tubers among
others potato varieties and consequently, a higher seed rate is
required to cover a hectare of land and also growers have
complaints that big sized tubers could take longer time for
cooking. In addition to plant spacing, time of harvesting in
potato also have influence on tuber sizes as tubers develop in
different physiological time starting from tuber initiation to
bulking stage. Most farmers harvest potatoes when its vine
(haulm) is dead naturally, which could result in bigger sized
tubers particularly for ‘Belete’ variety. Therefore, the present
study was carried out to study the tubers’ size distribution of
variety ‘Belete’ in response to different plant spacing and
times of harvesting.
2. Materials and Methods
2.1. Description of the Study Area
The experiment was conducted at Bekoji and Kofele,
Southeastern Ethiopia during the main growing season in
2018 and 2019. Bekoji and Kofele are the two major potato
growing areas in Arsi zone of Oromia region which are about
52km apart and 227 and 250 km from Addis Ababa
respectively. The study areas are located at an altitude of
2800 and 2650 meter above sea level respectively. The
maximum and minimum temperature was 20.48 and 2.63
0
C;
20.48 and 3.34
0
C respectively. The study areas have acidic
and loam soils and the agro- climatic condition of the areas is
wet with 956.6 and 950.6 mm mean annual rain fall and both
have a uni- modal rainfall pattern with extended rainy season
from March to September. However, the peak rainy season is
from June to August.
Experimental materials, design and procedure
The study was conducted on the improved variety ‘Belete',
one of the dominant potato varieties in the production system
in Ethiopia, originally released from Holeta Agricultural
Research Center in 2009 [13]. Twelve treatment
combinations of four plant spacing (75cmx30cm,
75cmx20cm, 60cmx30cm and 60cmx20cm) and three
harvesting time (90, 105 and 120 days after planting) were
laid out in a 4x3 factorial arrangement using Randomized
Complete Block Design (RCBD) in three replications.
Medium sized seed tubers (35-55mm) were planted per plot
(9m
2
) for each treatment combination based on the spacing
treatments mentioned above. The required agronomic
practices such as cultivation (weeding), ridging, fertilization,
pesticide application, etc. were applied to all experimental
units. Fertilizers were applied at the rate of 242kg ha
-1
NPS
and 150kg ha
-1
Urea, in which Urea is applied in split
application, half dose at full emergence and the rest half after
45 days depending on the fertility level of the soil. Late
blight disease (Phytophtora infestans) occurred on the
experimental fields was managed with Redomil and
Mancozeb.
2.2. Data Collected
The data was collected on tuber yield and yield related
traits such as number of main stem per hill, 50% stem height,
marketable tubers yield t ha
-1
, Small size tuber yield t ha
-1
,
unmarketable tubers yield t ha
-1
and total tubers yield t ha
-1
and specific gravity.
2.3. Data Analysis
The collected data were subjected to Analysis of Variance
(ANOVA) using statistical analysis Software (SAS version
9.2, 2008). The mean separation was done using (LSD) test
at 5% probability level.
3. Results and Discussion
The combined analysis of variance revealed that, stem
American Journal of Bioscience and Bioengineering 2021; 9(1): 1-7 3
number, stem height, marketable yield, small size tubers,
unmarketable yield and total tuber yield were all significantly
(P<0.05) influenced by the main effects of time of
harvesting. However, spacing only affected potato
marketable and total yields per hectare. While the interaction
effect of the two factors brought about highly significant
(P<0.01) effects on total marketable yields per hectare.
Table 1. Main effect of spacing and harvesting time on stem number, stem height, marketable yield, small size tubers, unmarketable yield and total tuber yield
across locations and years grown at Bekoji and Kofele, South East Ethiopia in 2018 and 2019.
Spacing Stem number at
50% flowering
Stem height at
flowering
Marketable yield
t ha
-1
Small size tuber
yield t ha
-1
Unmarketable
yield t ha
-1
Total yield t
ha
-1
Specific
gravity
75cm*30cm 3.57 81.67 44.23b 4.14 9.07 53.31b 1.1
75cm*20cm 3.72 84.06 46.39b 4.42 10.62 57.07b 1.1
60cm*30cm 3.38 81.27 45.60b 4.32 10.06 55.94b 1.1
60cm*20cm 3.53 81.71 53.43a 4.42 10.53 63.97a 1.1
LSD (5%) NS NS 41.99 NS NS 50.49 NS
Harvesting time
90 3.44b 79.48b 42.36b 5.08a 12.97a 55.33b 1.1
105 3.94a 82.10ab 49.03a 4.20ab 7.23c 56.26b 1.1
120 3.28b 84.95a 50.84a 3.69b 10.02b 61.07a 1.1
LSD (5%) 0.38 3.45 36.37 8.72 17.17 43.73 NS
locations
Bekoji 3.93a 79.57b 45.71b 4.51 10.19 59.21 1.10
Kofele 3.17b 84.78a 49.12a 4.14 9.95 55.91 1.09
LSD (5%) 0.31 2.82 29.69 NS NS NS NS
CV (%) 26.62 10.41 18.97 49.91 42.17 18.79 1.12
LSD0.05 = least significant difference at 5%, CV (%) = Coefficient of variation. Means in the same column followed by the same letter (s) are not
significantly different.
3.1. Stem Number at 50% Flowering
The analysis of variance revealed that stem number of
potato were significant (P<0.05) due to main effect of time of
harvesting, but statistically non-significant with spacing
(P >0.05).
Numerically the highest (3.94) stem number was recorded
from 105 days after planting, while lowest (3.28) was
obtained from time of harvesting 120 days after planting, but
spacing was not significantly (P>0.05) affected stem number
per hill. Stem numbers were reduced at high plant density
level and increased significantly at lower densities. This
might be due to population density and competition effect for
recourse like sun light, nutrient and water. Some studies, for
example in which the relation between plant spacing and
growth were examined, the results showed an increase in
plant spacing to be accompanied by an increased stem length.
The increased branching at the wider spacing did not
compensate for fewer plants/m
2
. They attributed increased
branching at wider spacing to the availability of more space
at lower plant densities. More space meant that plants were
able to exploit the available nutrients in the soil and the
photosynthetic active radiation for growth than plants at close
spacing [14]. However, location has very highly significantly
affected (P<0.001) stem number per hill. The highest stem
number was recorded at Bekoji, while the lowest was
obtained at Kofele (Table 1). This could be due to
environmental factors, such as soil variability, altitudes etc.
At Bekoji, the soil is nitosol (red) or more acidic and has
high rain fall and nutrient availability. At Kofele the soil was
clay loam soil, water logged areas and high nutrient
availability.
3.2. Stem Height at 50% Flowering
The combined analysis of variance revealed that stem
height of potato was significantly (P <0.05) affected by main
effect of time of harvesting but not statistically affected by
both spacing and their interaction (Table 1).
Numerically the highest (84.95cm) stem height was
recorded at 120 days after planting. The shortest (79.48cm)
stem height was obtained from 90 days after planting. But
spacing was not significantly (P>0.05) affected stem height.
This contradicting result could be due to soil variability,
planting season, moisture levels, and variety response to
location, light energy, biotic factors or other environmental
factors affecting the influence of plant spacing. On the other
hand location has very highly significantly affected (P<0.01)
stem height. Numerically the highest (84.78cm) stem height
was recorded from Kofele location; while the shortest
(79.57cm) was obtained at Bekoji (Table 1). This could be
due to differences in environmental factors, soil variability,
altitudes and amount of rainfall between the locations. At
Bekoji the soil was nito soil (red) or more acidic and high
rain fall and nutrient availability.
3.3. Marketable Tuber Yield t ha
-1
The combined analysis of variance revealed that,
marketable tuber yield of potato were significant (P<0.05)
due to main effect of both time of harvesting and spacing
(Table 1), and very highly significant (P<0.001) with their
interaction on marketable tuber yield t ha
-1
.
The highest (50.84 t ha
-1
) marketable tuber yield was
obtained from 120 days after planting, while lowest (42.361 t
ha
-1
) marketable tuber yield was recorded from 90 days after
4 Demis Fikre Limeneh et al.: Effects of Plant Spacing and Time of Harvesting on Yield and Tuber Size Distribution of
Potato (Solanum tuberosum L) Variety Southeast Ethiopia
planting. This might be due to the fact that at full
maturity/physiological maturity, small size tubers grown in to
medium size tubers through increased photo assimilation,
metabolic processes including cell division, cell expansion,
respiration and photosynthesis. Time of harvesting in potato
have influence on tuber sizes as tubers develop in different
physiological time starting from tuber initiation to bulking
stage. However, an experiment conducted at Bekoji in 2017
showed that, there was a tendency that marketable tuber yield
was declining with delayed harvesting. This could be for the
very reason that potato tubers could increase bulking and
increased large sized tubers towards late harvesting (Figure
1). This was also in line with the decreasing numbers of
small sized tubers towards late maturity (Figure 2).
Figure 1. Response of marketable tuber yield to time of harvesting at Bekoji,
2017.
Figure 2. Response of small number of tubers (unmarketable) to time of
harvesting at Bekoji, 2017.
Similarly the marketable tuber yield t ha
-1
was affected by
spacing. Numerically the highest (53.43) marketable tuber
yield t ha
-1
was obtained at the narrow spacing of
60cmx20cm, while lowest value (44.28) marketable tuber
yield was recorded at the wider spacing of 75cmx30cm. The
highest marketable yield recorded at closer spacing is
attributed to more tubers produced at the higher plant
population per hectare. The result is analogous with the
findings of [15]; reported that increasing plant density
increases the tuber yield per plant. The findings of [16] also
reported that the combination of inter and intra spacing had
significant effect on number of marketable yield. In a related
study [17] reported that wider spacing produced few tubers
as it gave rise to few stems that could lead to high number
and possibly tubers, but closer spacing improved quality and
saleable yield. The present result is contradicting with [18]
highest marketable yield was obtained at the wider intra row
spacing of 30 cm whereas the lowest was obtained at closer
spacing of 10 cm. Our results are in line with what was found
by [19] in that increasing the planting density from 4.44 to
6.67 plants m
-2
significantly increased total and marketable
tuber yield by 5.21 and 4.67t ha
-1
. Our result showed that
increasing plant population from 75cmx30cm (4.4 plants/m2)
to 60cmx20cm (8.33plants/m2) increased marketable tuber
yield from 44.23 to 53.43 t/ha). As mentioned above on the
effect of time of harvesting on marketable yields, the study in
2017 at Bekoji explained that increasing plant population
significantly increased marketable tuber yields to until an
optimum point where marketable tuber yield started to
decline due to increased number of small number of tubers
(Figures 3 and 4).
Figure 3. Response of marketable tuber yield to plant spacing (plant
population) at Bekoji, 2017.
Figure 4. Response of small number of tubers to plant spacing (plant
population) at Bekoji, 2017.
The combinations of spacing (60cmx20cm) and 120 days
after planting resulted in better marketable potato yield per
hectare. The lowest mean marketable yield was recorded
from spacing of 60x30cm and 90 days after planting
treatments. The combinations of the spacing of 60cmx20cm
and 120 days after planting brought about 17.2% increments
in marketable yield per hectare over the of spacing
(70x30cm) and early harvesting such as 90 days after
planting (Table 2). The increased yield at higher densities
may be attributed to the higher ground covered with green
leaves earlier (earlier in the season, light is intercepted and
used for assimilation), fewer lateral branches being formed
and tuber growth starting earlier. To produce smaller tubers,
higher plant densities are needed than for the production of
American Journal of Bioscience and Bioengineering 2021; 9(1): 1-7 5
big tubers. Consistent with this suggestion, increased plant
population density increased yield due to more tubers being
harvested per unit area of land [20]. However, decreases in
total yields as a result of wider spacing were compensated for
in part by increased production of large-sized tubers and
decreased production of small-sized tuber. This is apparently
a result of reduced interplant competition, which leads to
increased production of total tuber numbers per plant and
increased average tuber size with wider seed piece spacing
[21]. This result is analogous with [18] highest marketable
yield was obtained at the wider intra row spacing of 20 cm
whereas the lowest was obtained at closer spacing of 10 cm.
According to [19] increasing the planting density from 4.44
to 6.67 plants m
-2
significantly increased total and marketable
tuber yield by 5.21 and 4.67t ha
-1
.
On the other hand location has very highly significantly
affected (P<0.001) marketable yield. Numerically the highest
(49.12 t ha
-1
) marketable tuber yield was obtained from
Kofele location; while the lowest (45.71 t ha
-1
) was recorded
from Bekoji location (Table 1 and Figure 1). This may be due
to differences in environment and edaphic factors such as
amount of rainfall and soil type.
Table 2. The interaction effect of days after harvesting and spacing on
marketable yields grown at Bekoji and Kofele in 2018 and 2019.
DAH Spacing Marketable yield t ha
-
1
75cmx30cm 41.94
de
90 75cmx20cm 41.94
de
60cmx30cm 38.38
e
60cmx20cm 47.17b
cd
75cmx30cm 44.86
cde
105 75cmx20cm 47.29
bcd
60cmx30cm 50.18
bc
60cmx20cm 53.81
ab
75cmx30cm 45.88
cd
120 75cmx20cm 49.92
bc
60cmx30cm 48.25
bcd
60cmx20cm 59.31
a
Mean 47.42
LSD (0.05) 69.05
CV (%) 18.60
LSD0.05 = least significant difference at 5%, CV (%) = Coefficient of
variation, DAH = days after harvesting. Means in the same column followed
by the same letter (s) are not significantly different.
3.4. Small Size Tuber Yield t ha
-1
The combined analysis of variance revealed that small size
tuber yield of potato were significant (P<0.05) due to the
main effect of time of harvesting, but spacing, locations and
their interaction did not show significant difference on small
size tuber yield t ha
-1
(Table 1).
Numerically the highest (5.08 t ha
-1)
small size tubers were
obtained from 90 days after planting, while the lowest (3.69 t
ha
-1
) was recorded from 120 days after planting. This might
due to early harvesting or discriminate harvesting of potato
before full matured/physiological maturity. Under sized
potato tuber yield increases, unmarketable yields also
increased. Before full maturity harvesting of potato disturbed
more photosynthesis in a general increment of most
metabolic processes including cell division, cell expansion,
and respiration activities were reduced. For this reason small
size tuber or unmarketable number and yields also increased.
This result was also supported by an experiment conducted at
Bekoji in 2017 showing a clear variation in amount of small
sized tubers between early and late harvesting (Figure 2).
Spacing and location were did not show significant
difference on small size tubers. This might be due to
population density and competition effect for recourse like
sun light, nutrient and water. This contradicting result could
be due to soil variability, planting season, moisture levels,
and variety response to location, light energy, biotic factors
or other environmental factors affecting the influence of plant
spacing. However, the same experiment conducted in 2017 at
Bekoji showed that like time of harvesting, spacing also
affected the amount of small sized tubers (Figure 4).
Increasing plant population increased small sized tubers per
unit area. This was due to the reason that plants compete for
different resources at higher population than at lower
population resulting more number of small sized tubers per
plant which could increase unmarketable tuber yields.
3.5. Unmarketable Yield t ha
-1
The combined analysis of variance revealed that
unmarketable tuber yield of potato were highly significant
(P<0.05) due to the main effect of time of harvesting, but
spacing, locations and their interactions did not show
significant difference on unmarketable tuber yields t ha
-1
(Table 1)
Numerically the highest (12.97 t ha
-1)
unmarketable tuber
yield was obtained from 90 days after planting, while the
lowest (7.23 t ha
-1
) was recorded from 105 days after
planting. This might due to early harvesting or discriminate
harvesting of potato before full matured/physiological
maturity and very small size tubers increases during early
harvesting of potato (Table 1, Figure 2). At late harvesting or
over maturity of potato, the very large tubers increases and
unmarketable potato yields increased. To increase the
marketability of potato yields, it is important to harvest at
optimum harvesting time like 105 days after planting (Figure
1). Early harvesting (90 days) however increased
unmarketability of potato tubers due to increased number of
small sized tubers while late harvesting also did the same due
to increased number of large tuber numbers, which are also
unmarketable as far as Belete variety is concerned. Spacing
and location were did not show significant difference on
unmarketable tuber yields (Table 1) This contradicting result
could be due to soil variability, planting season, moisture
levels, and variety response to location, light energy, biotic
factors or other environmental factors affecting the influence
of different plant spacing. Nevertheless, results of similar
experiment at Bekoji in 2017 showed that plant spacing
affected the unmarketability of Belete tubers by increasing
the number of small tubers per unit area (Figure 4).
Generally, plants grown at closer spacing produced high
unmarketable tuber yield than plants grown at wider plant
spacing. Increasing plant density also increased the yield of
6 Demis Fikre Limeneh et al.: Effects of Plant Spacing and Time of Harvesting on Yield and Tuber Size Distribution of
Potato (Solanum tuberosum L) Variety Southeast Ethiopia
unmarketable tuber yield. Closer plant spacing increased
competition of plants for growth factors due to high number
plant per unit area than wider plant spacing which led to
producing high number of under size tubers which was high
unmarketable tuber yield [22].
3.6. Total Tuber Yield t ha
-1
The main effect of harvesting time and Spacing showed a
very highly significant (P<0.001) differences on total tuber
yield per hectare (Table 1). The highest (61.07 t ha
-1
) total
tuber yield was obtained from 120 days after planting, while
lowest value (55.33 t ha
-1
) was recorded from 90 days after
planting. This might be due to the fact that at full
maturity/physiological maturity, small size tubers get bulked
to medium/ large sized tubers which could increase the total
tuber yield. On the other hand the low tuber yields at early
harvesting time could be attributed to more number of under
sized and immature tubers.
Similarly the highest total tuber yield (63.97 t ha
-1
) was
obtained from the narrow spaced population (60cmx20cm)
whereas the lowest (53.30 t ha
-1
) was recorded at the wider
spaced population (75cmx30cm) in which yield increased
with increased plant population (Table 1). In other words, it
was clearly evident from the results that the total tuber yield
ha
-1
was increased with decreasing plant spacing. These
results are completely in agreement with [19] in that,
increasing the planting density from 4.44 to 6.67 plants m
-2
significantly increased total and marketable tuber yield by
5.21 and 4.67 t ha
-1
.
3.7. Correlation of Agronomic, Yield and Yield Components
of Potato
The correlation values explain the apparent association of
the agronomic and yield parameters with each other and
clearly indicated the magnitude and directions of the
association and relationships. Marketable yield of potato was
positively and highly significant correlated with stem number
and stem height at flowering (r = 0.194*) and (r = 0.409**)
respectively. This similarly implied that the increment of
stem number and height per plant caused for the increment of
marketable yield of potato. Total yield of potato per hectares
was positively and highly significant correlation was
observed stem number per plant (r = 0.207**), stem height (r
= 0.419**), Marketable yield (r = 0.905**), small size tuber
(r = 0.336**), and total unmarketable yield per hectare (r =
0.531**) (Table 3).
Table 3. Pearson Correlation among agronomic and yield components of potato crops across locations and years grown at Bekoji and Kofele, South East
Ethiopia in 2018 and 2019.
SNF SHF MTY SSTY TUMTY TY SPG
SNF 1
SHF 0.00980 1
MTY 0.194* 0.409** 1
SSTY 0.294** 0.078 0.189* 1
TUMTY 0.095 0.164* 0.120 0.408** 1
TY 0.207* 0.419** 0.905** 0.336** 0.531** 1
SPG 0.099 0.109 0.077 0.239** 0.359** 0.219** 1
* & ** Significant at 5% and 1% probability levels, respectively. The decimal numbers without any asterics are non-significant (P>0.05), SNF-Stem number at
flowering, SHF=Stem height at flowering, MTY=Marketable yield, SSTY=Small size tuber yield, TUMTY= Total unmarketable yield, TY= Total yield, SPG=
Specific gravity.
4. Conclusion and Recommendations
In conclusion, the plant spacing of 60cm x 20 cm
(83,333plants/ha) and harvesting 120 days after planting
resulted in the production of the highest marketable and total
tuber yields on Belete variety than any other treatments
studied. The spacing 60cmx20cm (83,333plants ha
-1
) brought
about 17.2% increments in marketable yield per hectare over
the generally recommended spacing of potato (75cmx30cm,
44,444plants/ha). From this study, therefore, it can be
recommended for Belete that the narrow spacing of
60cmx20cm and harvesting 120 days after planting could be
the optimum spacing and time of harvesting to produce
marketable tubers.
Acknowledgements
The authors acknowledge Ethiopian Institute of Agricultural
Research (EIAR), Kulumsa Agricultural Research Center
(KARC) for financial support and facilitation. The authors are
also grateful for researchers and technicians of potato research
program at Kulumsa Agricultural Research Centers and Bekoji
and Kofele sub sites for their contribution for the successful
accomplishment of this study.
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