Field trials were conducted at Tambul in the High Altitude Research Centre in Papua New Guinea Highlands. The trials evaluated four varieties of potato, two of which are resistant to Potato Late Blight disease and bred by the International Potato Centre (E2, E24), Kumdi and PNG industry variety, Sequoia against three planting densities (PD) and three fertilizer rates (FR) in a 4x3x3 factorial design. Trials were replicated three times and repeated in three seasons at three different sites. Stem height of E24 was significantly (P<0.05) higher followed by E2, Kumdi then Sequoia respectively. Marketable and total tuber number plant-1 was significantly (P<0.05) influenced by varieties and treatments especially PD. All varieties performed high marketable and total tuber number plant-1 at moderate to low PD. Optimum marketable and total tuber yield (t ha-1) of E2, Kumdi, Sequoia and E24 were observed at high PD and moderate to high FR. High seed tubers were observed at high density and low to moderate FR. E2 and Kumdi had appropriate genetic traits resistant to PLB disease and natural aptitude to influence tall stem height cultivated using high PD and moderated to high FR resulted in healthy crop development and high yield performance.

1. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Stem Height and Yield Response of Four Potato Varieties
to Planting Density and Fertilizer in Tambul, Western
Highlands Province, Papua New Guinea
Jonah Anton1*, Kud Sitango2 and Arthur Roberts3
1,2National Agriculture Research Institute, P.O. Box 120, Tambul, Western Highlands Province, PNG
3National Agriculture Research Institute, P.O. Box 4415, Lae, Morobe Province, PNG
Field trials were conducted at Tambul in the High Altitude Research Centre in Papua New Guinea
Highlands. The trials evaluated four varieties of potato, two of which are resistant to Potato Late
Blight disease and bred by the International Potato Centre (E2, E24), Kumdi and PNG industry
variety, Sequoia against three planting densities (PD) and three fertilizer rates (FR) in a 4x3x3
factorial design. Trials were replicated three times and repeated in three seasons at three different
sites. Stem height of E24 was significantly (P<0.05) higher followed by E2, Kumdi then Sequoia
respectively. Marketable and total tuber number plant-1
was significantly (P<0.05) influenced by
varieties and treatments especially PD. All varieties performed high marketable and total tuber
number plant-1
at moderate to low PD. Optimum marketable and total tuber yield (t ha-1
) of E2,
Kumdi, Sequoia and E24 were observed at high PD and moderate to high FR. High seed tubers
were observed at high density and low to moderate FR. E2 and Kumdi had appropriate genetic
traits resistant to PLB disease and natural aptitude to influence tall stem height cultivated using
high PD and moderated to high FR resulted in healthy crop development and high yield
performance.
Keywords: Fertilizer rate, Planting density, Potato varieties, Stem height, Tuber yield
INTRODUCTION
The Irish Potato (Solanum tuberosum) is an important crop
widely grown both for food and cash income at high-
altitude locations (1600-2800m above sea level) in Papua
New Guinea (PNG). The production of potato for formal
trade in the country using Sequoia is undertaken largely by
smallholder farmers with farm size of less than a hectare
(0.1- 0.3 ha). Production is estimated to be around 15,000
tons annum-1 from 1,000 ha averaging about 15 tons ha-1
valued at about PGK10 -15 million at farm gate (FPDA
Annual Report, 2013; Pitt and Wicks, 2003).
Potato production in developing countries is hampered by
constraints including low soil fertility, pests, disease and
inadequate supply of good seed quality (FAO, 2009).
Okrupa et al. (2017) identified that pest and disease was a
major constraint in potato production in PNG. The
infestation of Potato Late Blight (PLB) disease caused by
Phytophthora infestans caused considerable damage to
potato production in the PNG highlands in 2003,
particularly for the most commonly grown commercial
variety, Sequoia (Minemba and Kerru, 2014). This reduced
the livelihood of potato growers at high altitude locations,
reducing both food supply and their cash income. In
response to the incursion of the disease, an integrated
disease management package and four potato clones
(E24, E2, E11 and E20) showing high levels of resistance
to the causal agent of PLB were released in 2011 and
2013, respectively. The introduced varieties were reported
to have similar yield levels to the industry standard,
Sequoia (Minemba and Kerru, 2014). However, farmers in
Alkena and Kiripia communities in Tambul District claimed
that the released clones had a lower tuber weight
compared to Sequoia. This reduced their cash income and
*Corresponding Author: Jonah Anton, National
Agriculture Research Institute, P.O. Box 120, Tambul,
Western Highlands Province, Papua New Guinea. Email:
jonahanton986@gmail.com, jonah.anton@nari.org.pg
Research Article
Vol. 6(1), pp. 092-098, May, 2020. © www.premierpublishers.org, ISSN: 3369-9526
International Journal of Horticultural Science and Ornamental Plants

2. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Anton et al. 093
hence farmers preferred to continue growing Sequoia
despite the need to purchase and apply fungicides two to
five times a week.
Many factors influence potato tuber yield and quality
including cultivar, plant population, soil type, pests,
disease and fertilization input (Khalafalla, 2001; Mangani
et al., 2015; Wiles, 2000). Planting density and fertilizer
input are the two most important agronomic practices in
potato production as they strongly influence plant
development, yield and quality of the crop (Lamessa and
Zewdu, 2016; Mangani et al., 2015). Manipulating plant
population affects the size of the resulting tubers (Bussan
et al., 2007) while fertilizer application rate determines
tuber yield and quality (Mishra, 2018). Minemba and Kerru
(2014) reported that they used a standard planting density
(31,250 plants ha-1) and fertilizer application rate (1,200kg
ha-1) for Sequoia variety in all International Potato Center
(CIP) varieties evaluation trials. Kerru stated in RU-ARD
project Technical Report that farmers currently growing
released CIP clones were using standard density and
fertilizer rate for Sequoia. Therefore, the objective of the
study done was to determine which combination of
planting density and fertilizer rate optimizes stem height,
yield and quality of four potato varieties.
MATERIALS AND METHODS
Site description
The trials were conducted in the high-altitude ecological
zone at approximate coordinates of 05°52’50.7 S,
143°56’57.5 E. Trial season one was implemented on-
farm at Yawar about 2,400 meters above sea level (masl)
in a sandy loam volcanic ash soil with pH 5.0 to 6.0
(Sawanga, 1991). Mean total production rainfall of 374.3
mm was recorded from a Nylex rain gauge during the trial
period from July to November, 2015.
Trial season two was implemented on-station at National
Agriculture Research Institute (NARI) in Tambul from
February to May in 2016. Trial season three was also
implemented on-station from March to July in 2016. Both
trials were conducted at an altitude of 2,320 masl. Total
rainfall over the growing seasons were 827 mm and 752
mm for season two and season three respectively.
Potato varieties
Four potato varieties; E2, E24, Kumdi and Sequoia were
selected for the study. Varieties E2 and E24 were part of
59 clones imported from Peru (International Potato Center)
for evaluation and released by NARI in 2011 based on their
level of resistance to PLB pathogen and yield performance
(Minemba and Kerru, 2014). Kumdi is a local potato variety
identified in a farmer’s field at Kumdi in Western Highlands
Province (WHP) in 2005 and it is currently under research
(Anton et al., 2018). The commonly grown variety Sequoia,
which is high susceptibility to PLB pathogen (Minemba and
Kerru, 2013; Anton et al., 2018) was selected has as a
control variety. The planting materials of these four
varieties were sourced from Fresh Produce Development
Agency (FPDA) and NARI for trial season one. Seeds
generated from season one was used in season two and
season three.
Trial design
The experiment was designed in a 4 x 3 x 3 factorial
arrangement fitted into a split-plot layout. Factor one was
four potato varieties (E2, E24, Kumdi and Sequoia) and
factor two was nine treatment combinations of three
planting densities (60x25cm, 70x30cm and 80x40cm) and
three potato mix fertilizer application rates (1,200kg ha-1,
1,700kg ha-1 and 2,200kg ha-1) with three replications
(Table 1).
Table 1: Nine treatment combinations of potato planting
density and fertilizer application rate matrix used in the
trials.
Fertilizer
rates (FR)
Planting densities (PD)
66,667
plants ha-1
(high PD)
47,619 plants
ha-1
(moderate PD)
31,250
plants ha-1
(low PD)
1,200kg ha-1
(low FR)
Treatment 1 Treatment 4 Treatment
7
1,700kg ha-1
(moderate
FR)
Treatment 2 Treatment 5 Treatment
8
2,200kg ha-1
(high FR)
Treatment 3 Treatment 6 Treatment
9
Note: Treatment 7 was a control treatment having
standard or commonly used PD and FR for comparison.
The main plot was 50.4 m2 and the area for each split-plot
treatment was 5.8 m2 occupying 36 plants in high density,
24 plants in moderate density and 18 plants in low density.
The area of each replicate was 201.6 m2 and total area for
three replicates was 604.8 m2.
Planting and management practices
Land was prepared manually using spades and seeds
were planted in rows made according to planting densities.
Potato mix fertilizer (N =10%, P = 25%, K = 12% and MgO2
= 2%) was calculated and manually applied according to
the weight for each treatment. Normal management
practices recommended by Minemba and Kerru (2014)
were applied across all seasons.
Data collection
Stem heights were measured from the ground level to the
last opened leaf at maturity stage. Tuber yields for each
variety were recorded as tuber number plant-1 and tuber
weight (g) plant-1 in the following categories; marketable
(>100 grams), seed (20 – 99 grams), mini-tubers (<20
grams) and damaged (Minemba and Kerru, 2014). Tuber
weight was converted to tons ha-1 for analysis.

3. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Int. J. Hort. Sci. Ornam. Plants 094
Data analysis
The collated data from each variable were sorted using
Microsoft Excel (2007). An analysis of variance used a
split-plot statistical design to detect significant differences
at P-value of 5 percent using GENSAT Discovery Version
3. Upon detection, a means separation test using Fisher’s
Least Sum of Squares (LSD) was used for analysis to
detect significance differences among variable means.
RESULTS
Stem height
Highly significant differences (P<0.05) were detected for
stem height at maturity among the four varieties (Table 2).
E24 was significantly taller (63 cm) followed by Kumdi (52
cm), E2 (49 cm) and Sequoia (31 cm) respectively.
Treatment means averaged over varieties were not
significantly different, but there was a significant
interaction (P<0.05) between treatments and varieties.
However, the ranking of the varieties for stem height at
maturity remained mostly the same regardless of
treatment (Table 2). Generally, variety E24 had statistically
similar and high stem height across all treatments followed
by Kumdi with similar stem height across all treatments.
Sequoia had lowest stem height across all treatments
compared to the stem height of other varieties across
treatments.
Table 2: Stem height (cm) at 64 DAP (maturity stage) of four potato varieties evaluated against nine treatment
combinations of PD and FR. Treatment 7 is a control treatment.
Treatment (T) combinations of planting density and fertilizer rate
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode High3
E2 46cd 51de 51de 52d 54ef 50c 43c 52de 43c 49b
E24 61ghi 65i 66i 62ghi 61ghi 64i 63hi 60fghi 63h 63d
Kumdi 52de 57efg 51de 50ce 53e 55efg 53e 54ef 46cd 52c
Sequoia 28a 30ab 29ab 35b 36b 27a 32ab 32ab 34ab 31a
Mean 47 51 49 50 51 49 48 49 46
Factor LSD F (P<0.05) CV (%)
Variety 2 * 3.4
Treatment n/s n/s 3.4
Variety x Treatment 7 * 8.8
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non significant
Tuber number per plant
Marketable tuber plant-1
Marketable tuber number plant-1 was significantly (P<0.05)
affected by varieties and treatments (Table 3). Variety E2
and Sequoia yielded twice as many (P<0.05) marketable
tuber numbers plant-1 as E24 and Kumdi. Marketable tuber
number plant-1 was greater (P<0.05) for the moderate and
low planting densities than for the high planting density.
Low PD and moderate FR (Treatment 8) yielded the
highest tuber number plant-1 compared to other
treatments. The highest PD (Treatment 1, 2 and 3) yielded
the lowest marketable tuber number plant-1 and the
moderate to low PD (Treatment 4, 5, 6, 7, 8 and 9) resulted
in high marketable tuber numbers. There was no
significant (P>0.05) interaction between varieties and
treatments on marketable tuber number plant-1.
Table 3: Marketable tubers plant-1 of four potato varieties evaluated against nine treatment combinations of PD and FR.
Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode High
E2 1 2 2 2 2 2 2 4 2 2b
E24 1 1 1 2 1 1 2 2 2 1a
Kumdi 1 1 1 2 1 1 2 2 2 1a
Sequoia 1 1 2 2 2 2 3 2 3 2b
Mean 1a
1a
1a
2b
2b
2b
2b
3c
2b
Factor LSD F (P<0.05) CV (%)
Variety 1 * 16.9
Treatment 2 * 16.9
Variety x Treatment n/s n/s 20.2
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non-significant.

4. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Anton et al. 095
Seed tuber plant-1
Varieties differed significantly (P<0.05) for mean seed
tuber number plant-1 whereas treatments had no
significant (P>0.05) effect on seed tuber number plant-1
when averaged over varieties (Table 4). Variety E2 yielded
significantly (P<0.05) more seed tubers than the other
three varieties and E24 and Kumdi yielded more seed
tubers than Sequoia. Varieties E24 and Kumdi seed tuber
yields were statistically similar. There was also no
significant interaction between varieties and treatment
combinations of PD and FR.
Table 4: Seed tubers plant-1 of four potato varieties evaluated against nine treatment combinations of PD and FR.
Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode High
E2 5 5 5 5 6 5 6 6 5 5c
E24 4 4 4 4 4 4 5 4 4 4b
Kumdi 4 4 4 4 5 4 4 4 5 4b
Sequoia 3 3 3 3 3 2 3 3 4 3a
Mean 4 4 4 4 4 4 5 4 5
Factor LSD F (P<0.05) CV (%)
Variety 1 * 15.4
Treatment n/s n/s 15.4
Variety x Treatment n/s n/s 24.1
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non significant
Total tuber plant-1
Variety E2 yielded significantly more (P<0.05) total tuber
number plant-1 than the other three varieties (Table 5).
Varieties E24 and Kumdi total tuber yields were
statistically similar and both yielded significantly (P<0.05)
greater than total tuber number of Sequoia. Low PD and
low to high FR (Treatment 7, 8 and 9) yielded statistically
similar but low PD and high FR (Treatment 9) was
significantly (P<0.05) greater than the other six treatments.
Treatment 1 yielded statistically similar to Treatments 2, 3,
4, 5 and 6 but significantly lower when compare with
Treatments 7, 8 and 9 (Table 5).
Table 5: Total tubers plant-1 of four potato varieties evaluated against nine treatment combinations of PD and FR.
Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode High
E2 9 10 10 9 10 11 12 13 11 11c
E24 8 8 8 7 7 8 9 9 10 8b
Kumdi 6 7 7 8 8 8 8 8 9 8b
Sequoia 6 6 6 7 7 7 8 7 9 7a
Mean 7a
8ab
8ab
8ab
8ab
8ab
9bc
9bc
10c
Factor LSD F (P<0.05) CV (%)
Variety 1 * 9.7
Treatment 1 * 9.7
Variety x Treatment n/s n/s 15.9
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non significant.
Tuber yield tons per hectare
Marketable tuber yield (t ha-1
)
Marketable tuber yield of varieties E2, Kumdi and E24
were statistically similar but Kumdi was significantly
(P<0.05) higher than Sequoia (Table 6). Yields of varieties
E2, E24 and Sequoia were statistically similar. Treatment
3 representing the highest PD and highest FR yielded
significantly (P<0.05) better than any of the other eight
treatments when averaged over the varieties. Treatment 5
and 6 respectively representing moderate PD and
moderate to high FR respectively and Treatments 8 and 9
representing low PD and moderate to high FR respectively
resulted in the next highest yields. Treatment 2 (high PD
and moderate FR), 4 (Moderate PD and Moderate FAR)
and 7 (low PD and low FR) were statistically similar and
significantly higher than Treatment 1 (high PD and low
FR).

5. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Int. J. Hort. Sci. Ornam. Plants 096
Highly significant (P<0.05) interactions were observed
among the individual combinations of varieties and
treatments. Kumdi was clearly greatest at the highest PD
and highest FR (Treatment 3). In fact, the yield for
Treatment 3 for this variety was numerically superior to any
other combination of variety and treatment. Sequoia was
statistically similar across most of the treatments, as was
for E24.The highest marketable tuber yields for E2 and
Kumdi occurred at the two highest fertilizer rates for each
plant density.
Table 6: Marketable tuber yield (t ha-1) of four potato varieties evaluated against nine treatment combinations of PD and
FR. Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode Mode
E2 3.69ab 7.33cde 10.55efg 4.41abc 9.50defg 10.08efg 5.82bcd 9.41defg 10.27efg 8.01ab
E24 5.85bcd 7.86cde 7.32cde 6.35bcd 8.34cdf 8.45def 8.08cde 9.80def 8.87cdef 7.88ab
Kumdi 5.88bcd 8.01cde 15.86h 10.15efg 11.46fg 11.83fg 8.43df 10.37efg 12.42g 10.49b
Sequoia 1.97a 4.01ab 7.85cde 6.06bcd 5.18abc 6.77bcd 4.55abc 6.20bcd 2.78a 5.04a
Mean 4.35a
6.80b
10.65d
6.74b
8.62c
9.28c
6.72b
8.95c
8.58c
Factor LSD F (P<0.05) CV (%)
Variety 3.86 * 17.8
Treatment 1.30 * 17.8
Variety x Treatment 3.56 * 19.0
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05.
Seed tuber yield (t ha-1
)
Seed tuber yield was not significantly (P>0.05) affected by
varieties nor was there a significant interaction between
varieties and treatments (Table 7). However, it was
significantly (P<0.05) affected by treatments, averaged
over varieties. Yields in high PD (Treatments 1, 2 and 3)
were statistically similar but Treatment 1 and 2 were
significantly (P<0.05) higher than the other six treatments
(moderate to low PD). There was a linear relationship
between density and seed tuber yield. Seed tuber yield
increased as PD increased from low to high density. Figure
1 illustrated this linear relationship between seed tuber
yield and PD. Fertilizer had less significant influence on
seed tuber yield.
Figure 1: A scatter graph with a trend line illustrating a
linear relation between seed tuber yield and density in nine
treatments mean. Seed tuber increased as density
increases.
Table 7: Seed tuber yield (t ha-1) of four potato varieties evaluated against nine treatment combinations of PD and FR.
Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode Mode
E2 16.73 13.53 12.58 13.18 13.15 10.21 10.28 9.05 9.37 12.01
E24 14.49 12.95 14.60 13.14 11.73 10.81 11.62 8.02 10.05 11.93
Kumdi 15.95 15.03 9.15 11.06 11.26 10.35 10.72 8.05 8.12 11.14
Sequoia 10.21 9.49 8.81 8.69 6.74 6.24 8.03 7.46 6.85 8.06
Mean 14.35fe
12.75e
11.28de
10.67cd
10.72cd
9.40abc
10.16bcd
8.15a
8.60ab
Factor LSD F (P<0.05) CV (%)
Variety n/s n/s 15.6
Treatment 1.67 * 15.6
Variety x Treatment n/s n/s 17.8
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non significant.

6. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Anton et al. 097
Total tuber yield (t ha-1
)
There were significant differences (P<0.05) in total tuber
yield among four varieties and nine treatments (Table 8).
Yield of E2, Kumdi and Sequoia were statistically similar
but E2 and Sequoia yielded significantly (P<0.05) higher
than E24. Yield of E24 and Kumdi were statistically similar.
Highly significant differences (P<0.05) were also detected
among nine treatments combination of PD and FR (Table
8). High PD and high FR (Treatment 3) significantly out-
yielded the other eight treatments, followed by Treatment
2 (high PD and moderate FR) and 5 (moderate PD and
moderate FR). Treatments 1, 4, 6, 7, 8 and 9 were
statistically similar and yielded lower than treatment 2, 3
and 5. There was no significant (P<0.05) interaction
between varieties and treatment combinations (Table 8).
Table 8: Total tuber yield (t ha-1) of four potato varieties evaluated against nine treatment combinations of PD and FR.
Treatment 7 was a control treatment.
Treatment 1 2 3 4 5 6 7 8 9
Density High High High Mode Mode Mode Low Low Low
MeanFertilizer Low Mode High Low Mode High Low Mode Mode
E2 29.48 36.21 42.90 28.31 30.78 30.12 28.91 30.80 25.07 31.40b
E24 24.91 29.60 31.82 23.63 28.73 23.74 23.14 24.43 27.32 26.37a
Kumdi 28.09 33.06 41.74 27.50 29.95 29.59 24.38 25.06 25.18 29.40ab
Sequoia 28.73 36.77 42.32 35.75 34.42 32.84 31.50 29.20 28.46 33.33b
Mean 27.80ab
33.91c
39.70d
28.80ab
30.97bc
29.07ab
26.98a
27.37a
26.51a
Factor LSD F (P<0.05) CV (%)
Variety 5.01 * 8.3
Treatment 3.59 * 8.3
Variety x Treatment n/s n/s 14.6
Note: Mode = Moderate; The mean not sharing a common letter in a column and row differ significantly at 0.05; * =
Significant at P<0.05. n/s = non significant
DISCUSSION
Tuber number plant-1
The differences in tubers number plant-1 were significantly
affected by varietal differences and treatment effects from
PD and FR. Mangani et al. (2015) stated that different
varieties have different capacities of producing different
tuber number and size. The results from this study showed
that variety E2 had genetic traits influenced high
marketable and seed tubers resulted in high total tuber
number plant-1. Minemba and Kerru (2014) also
documented that E2 yielded high marketable, seed and
total tubers plant-1 compared to E24 and Sequoia in their
potato varieties evaluation trials in the Highlands. Stem
height had relationship with seed and total tuber number
plant-1 of four varieties. Varieties E24, E2 and Kumdi had
high stem heights (Table 2) resulted in high seed (Table 4)
and total tuber number plant-1 (Table 5) compared to the
stem height and yield of Sequoia variety.
Treatment differences were significantly affected by PD.
Tuber number decreased as PD increased, most likely
because of increased competition between plants for
nutrients, water and sunlight (Taheri and Shamabadi,
2013). High tuber number plant-1 occurred at low PD
whereas low tuber plant-1 occurred at high PD (Minemba
and Kerru, 2014). FR does not have significant influence
on tuber yielded plant-1 of four varieties.
Tuber yield (t ha-1
)
The tuber yield differences in four potato varieties were
significantly affected by varietal differences and treatment
combinations of PD and FR. This confirms the conclusion
made by Mangani et al. (2015) that different varieties have
different capacities of producing different tuber yields (t ha-
1). High photosynthesis rates (not measured) were
assumed in varieties E2 and Kumdi due to their tall stem
heights (Table 2), high canopy, healthy development
resulted in high marketable, seed and total tuber yield
compared to the yield of Sequoia and E24 (Vandermeiren
et al., 2005). Mangani et al. (2015) also asserted that tuber
yield of potato crop was significantly influenced by the
genetic make-up of each variety which confirmed in this
trial. E2 and Kumdi out-yielded Sequoia and E24 is agreed
with the marketable yield result presented by Minemba
and Kerru (2014) and Anton et al. (2018). Farmers in
Alkina and Kiripia reported that marketable yield and cash
income received for varieties E2, Kumdi and E24 were
lower compared to Sequoia. However, results from this
trial showed that E2 and Kumdi performed better than
Sequoia using appropriate agronomic input. Lamessa and
Zewdu (2016) and Mangani et al. (2015) reported that PD
and FR are the two most important agronomic practices in
potato production management as they strongly influence
the plant development, yield and quality of the crop. High
marketable, seed and total tuber yield were observed at
high PD (66,667 plants ha-1) and moderate to high FR
(1,700 – 2,200kg ha-1) which confirmed the results
presented by Lamessa and Zewdu (2016). Generally,
marketable yields were significantly influenced by fertilizer
(Mishra, 2018) and seed tuber yield were influenced by
density (Table 7) which confirmed Khalafalla (2001) and
Wiles (2000) conclusions. E2 and Kumdi with genes
resistant to PLB and natural aptitude to influence tall stem
height, healthy crop development in responses to high PD
and moderate to high FR resulted in the high tuber yield
performance.

7. Stem Height and Yield Response of Four Potato Varieties to Planting Density and Fertilizer in Tambul, Western Highlands Province, Papua New Guinea
Int. J. Hort. Sci. Ornam. Plants 098
CONCLUSION
Potato crop development and tuber yield performance
were influenced by many factors such as cultivars, planting
density, fertilizer, pest, disease and climatic variations.
Among these factors, four varieties have been investigated
under three different levels of PD and FR. The results
showed that the stem height and tuber yields were
significantly influenced by varieties, PD and FR. The study
had statistically shown that different varieties have
different genetic characteristics that influenced stem
height, tuber number and tuber yield performances. High
marketable and total tuber yield (t ha-1) of Kumdi, E2,
Sequoia and E24 occurred with the highest PD (66,667
plants ha-1) and moderate to high FR (1,700kg ha-1 to
2,200kg ha-1). High seed tuber yield was indicated in
highest PD and low to moderate FR (1,200ka ha-1 1,700kg
ha-1).
Farmers in PNG including Alkina and Kiripia in Tambul are
recommended to use high PD of 66,667 plants ha-1 and
FR of 1,700 to 2,200kg ha-1 of the potato mix fertilizer to
optimize marketable and seed tuber yields for varieties E2,
Kumdi and E24 instead of using standard PD (32519 plant
ha-1) and FR (1,200kg ha-1). Different generation of
planting materials used in the trials and environmental
factors also affected the growth and tuber yield. Further
research into these findings using same generation of
planting materials and appropriate management is worth
pursuing.
ACKNOWLEDGEMENT
National Agriculture Research Institute is fully
acknowledged for the funding support. Special gratitude
and thanks to Prof. Bob Nielsen, Dr. Dom, Cyril Atung,
Stanley Amben, Jeremiah Ahizo and Tambul Centre
Management team for facilitating and providing the
necessary support.
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Citation: Anton J, Sitango K, Roberts A (2020). Stem
Height and Yield Response of Four Potato Varieties to
Planting Density and Fertilizer in Tambul, Western
Highlands Province, Papua New Guinea. International
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Copyright: © 2020. Anton et al. This is an open-access
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