American Journal of Plant Sciences, 2011, 2, 636-643
doi:10.4236/ajps.2011.25075 Published Online November 2011 (
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density
and Variety
Khalid El-Sayed Abd El-Hamed, Mohammed Wasfy Mohammed Elwan
Department of Horticulture, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt.
Received July 5th, 2011; revised August 29th, 2011; accepted October 4th, 2011.
Pumpkins (Cucurbita spp.) are an important specialty vegetable. Field studies were conducted on three pumpkin culti-
vars characterized with different growth habits to determine the effects of plant population and genotypes on market-
able yield. Increasing plant populations from 4780 to 9560 plant per hectare resulted in significantly greater fruit
number and yield in both growing seasons and for all tested genotypes. Average fruit weight declined at the higher
populations. The resp onse of pumpkin genotypes to different planting d ensities was genotype (growth habit) dependent
since the response was pronou nced in large vine types co mpared to bush type. Th e phenotypic variation existed among
pumpkin genotypes for yield seems to be under genetic control. Foliar application of potassium improved growth and
yield of pumpkin plants althou gh the non-significan t effect. These results demonstrate that growers may increase pump-
kin yield by increasin g pla nt p op ulat io ns.
Keywords: Cucurbita Pepo, Cucurbita Moschat a, Pumpkin, Planting Density, Plant Population, Competition,
Potassium, Cultivar by Environment Interaction
1. Introduction
The relationship between crop yield and planting density
(number of plant unit area) is of considerable agronomic
interest [1-3]. It is clear that the density-dependent ef-
fects on the yield are due to the competition between
adjacent plants for the necessary natural resources. There
is a basic assumption that a plant located at a given site is
constrained to draw nutrients only from its immediate
vicinity and this zone may be larger than the size of the
actual plant both on the surface and into the ground [4,5].
If a crop is grown at a range of plant densities, and all the
plants are harvested at one time, it is generally supposed
that the total dry matter yield per unit area will increase
with increasing density until a level of yield is reached
which is barely exceeded as density increase further. This
constant yield over a wide range of high density is
thought of as representing the maximum fixation of en-
ergy that crop can achieve in the time between sowing
and harvest [6]. Yield eventually reaches a plateau as
plant density increases to the point when crop yield be-
come unmarketable. Since competition between plants
greatly affect yield [3,7] it is therefore possible to adjust
size of the harvested crop to meet the requirements of the
market by manipulating density [8]. Plant population can
influence crop by pest interactions. For instance, closer
plant spacing may give crops competitive advantage over
weeds or provide ecological weed control. A key com-
ponent of alternative approaches to weed management
(other than chemical control) is the enhancement of crop
competitiveness against weeds [9]. Manipulation agro-
nomic factors such as row and plant spacing may provide
a non-chemical means of reducing the impact of weeds
interference on crop yields [10]. Leaf area increases and
light transmittance to the soil decreases as plant popula-
tion increases [11]. Decreased light transmittance through
the leaf canopy of crops planted in narrow rows or at
high populations could suppress growth and development
of weeds [12].
Increased plant density may discourage colonization
by certain insects or reduce percentage of insect-dam-
aged plants. While, in terms of disease pressure high-
density plantings may cause more rapid dissemination of
certain pathogens [12]. Also, closer rows and higher
plant populations reduced evaporation, increased effi-
ciency of water use and gave higher growth and yields by
increasing the energy available to the crop [13].
Pumpkin is commonly refers to cultivars of any one of
the species Cucurbita pepo, Cucurbita mixta, Cucurbita
Dependence of Pumpkin Yield on Plant Density and Variety637
maxima, Cucurbita moschata [14]. Pumpkin is popular
vegetable with high productivity, high nutritive value and
good storability. Pumpkin has good nutritive benefits
with balanced colories and is believed to be a good
source of carotenoids [15-17].
Plant density affects the growth and productivity of
numerous vegetable crops including cucurbits such as
squash [18,19], watermelon [20-23], muskmelon [24-29],
cucumber [30-35].
In pumpkin, Reiners and Riggs [36] reported a signi-
ficantly linear increase in the number of fruit per acre as
plant population increased from 1874 to 7495 plant/acre
in two different types of pumpkin cultivars (semi-vining
and large-sized vine). Increased plant population resulted
in a significantly linear decrease in average fruit size [36].
The same authors reported in a similar study a signifi-
cantly linear increase in yield of same cultivars as plant
population increased from 1210 to 3626 plants/acre [37].
Increased plant population resulted in increased number
of fruit per acre and decreased average fruit size. In-
creased number of fruit more than compensated for de-
creasing fruit weight and resulted in an overall increase
in yield [37]. Cushman et al. [8] reported that plant
population significantly affected pumpkin yield and yield
components associated with plant productivity (fruit
weight and size, number and weight of fruit per plant).
Plant spacing had no significant effect on color, handle
quality and shape of marketable pumpkins [38].
Pumpkin fruit is characterized by its large volume and
heavy weight which hinder the harvest and transportation
processes. The consumption of pumpkin is constrained
by the inappropriate size of the fruit to most of consu-
mers. Small-to medium-sized fruits may assist in spread-
ing of pumpkin between consumers. Pumpkin growers
are exploring ways to increase yield per unit area in order
to save on land and maximize profitability. Increasing the
number of plants per area with careful attention to nitro-
gen nutrition and variety may accomplish this goal.
Growers have two options when increasing plant popula-
tions per unit area, either within-row or between-row
spacing can be decreased.
Better understanding of genotype and environment in-
teraction will help to optimize yield and quality of crops.
Any individual organism is able to alter its morphology
and/or physiology in response to changes in environ-
mental conditions [39]. The higher the proportion of the
phenotypic variation attributed to the genotypic diffe-
rences, the greater the feasibility of genetic manipulation
to improve crop performance. Partitioning of phenotypic
variance requires evaluating performance of genotypes in
a range of environments (years and/or locations).
Since competition between plants for water and nutri-
ents such as potassium deeply affect yield [3], the heal-
thy nutritional status of the plants can reduce competition.
If potassium is deficient or not supplied in adequate
amounts, growth is stunted and yields are reduced [40].
Potassium is associated with movement of water, nutri-
ents and carbohydrates in plants. The relation between
potassium and fruity vegetables such as pumpkin is well
established long time ago [41]. There is increasing evi-
dence from the literature that optimizing the potassium
nutritional status of plants can reduce the detrimental
build up of reactive oxygen species (ROS) which result
from various environmental stress factors [40]. In addi-
tion, it is widely acceptable that in general, high potas-
sium status in crops decreases the incidence of diseases
and pests [42].
The objectives of this research were to determine the
effect of altering plant population by varying in row
spacing while holding between row spacing constant on
the yield of three pumpkin varieties of different growth
habit (bush-type vs. vine type).
2. Materials and Methods
2.1. Experimental Set up
Field experiment was conducted at the Experimental Re-
search Farm, Faculty of Agriculture, Suez Canal Univer-
sity, Ismailia, Egypt. The experiment was carried out in
spring-summer season of 2010 and was repeated in
spring-summer season of 2011. The soil of the experi-
mental site was sandy soil (82.21% sand, 11.5% silt and
3.29% clay) with pH 8.27 and EC 0.47 dsm–1. Before
each planting, the experimental location was prepared
three months before transplanting. During preparation, a
rate of 48 m3 of cattle manure plus 700 kg calcium super-
phosphate (15.5% P2O5) per ha was supplemented, then
the soil of the site was cleared, ploughed, harrowed and
divided into plots. Each genotype occupied three rows
per replicate, each row represents one of the spacing
treatments and each row was 10 m in length and 2 m
width containing 10, 15 and 20 plants. Three different
plants spacing of 1, 0.75 and 0.5 m were used for each
genotype in each replicate. Weeds were controlled using
cultivation and hand weeding. Insect and disease pres-
sure was monitored and protective treatments applied
when warranted. A one-time harvest was made when
fruits reached marketable ripening stage, counted and
weighted. Only fruit that were representative to the cul-
tivars, firm and free from major blemishers or rot were
considered marketable.
2.2. Plant Materials
Pumpkin genotypes were “Frosty F1” (Cucurbita pepo),
“Dicknson F1” (Cucurbita moschata) and “Pro-gold F1
(Cucurbita pepo). Seeds of pumpkin genotypes were
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density and Variety
sown in 84-cell styrophom trays under greenhouse con-
ditions. The trays were filled with soil mixture (Peat
moss and vermiculite mixes in 1:1 v/v, enriched with
different nutrients). After emerging, seeds were watered
with a commercial nutrient solution (19-19-19 N-P-K)
with micronutrient at a dilution of 1:200. The seedlings
were maintained in the greenhouse under high humidity
and with day/night temperature of 30/20˚C for four
weeks. Pumpkin seedlings, four weeks old were trans-
planted from the mid of February to the end of May in
both seasons.
2.3. Potassium Foliar Application
In the second experiment the plants of genotypes “Frosty”
and “Dickinson” were sprayed with KNO3 at a concen-
tration of 10 mM/l. Potassium nitrate was applied three
times during flowering and fruiting stages with one week
interval. The volume of sprayed solution ranged from 50
to 100 ml per plant each time, depending on plant size or
development. The same amount of water was pulverized
to the control plants. The pH was measured for water and
KNO3 solutions and adjusted to 7.0. All theses sprays
were applied in the morning (8.00 - 9.00 a.m.).
2.4. Statistical Analysis
The experiment was laid-out in a Randomized Complete
Block Design (RCBD) with three replications. Data were
statistically analyzed using ANOVA/MANOVA of Sta-
tistica 6 software (Statsoft, [43], Tulsa, Ok, USA) with
mean values compared using Duncanś multiple range
with a significance level of at least p 0.05.
3. Results
3.1. The Effect of Planting Density
The effects of planting population on fruit weight and fruit
yield in three different genotypes of pumpkin in both
growing seasons are presented on Table 1. Increasing the
plant population from 4780 to 9560 plant/ha by decreas-
ing the in row spacing from 1.0 m to 0.5 m significantly
decreased the fruit weight in genotype “Pro-gold” (large
vine type) while it did not show any effect on the other
two genotypes in the first season. In the second season
the performance of genotype “Frosty” (push type) was
not changed comparing with the first season while the
other two large vine type genotypes showed slightly dif-
ferent performance than first season.
The high density population showed significantly dif-
ferent fruit weight in genotype “Dickinson” (large vine
type) while genotype “Pro-gold” showed less pronounced
differences than the first season. In accordance with pre-
vious research, the fruit weight reduction associated with
increasing population density was compensated by the
increasing in the number of fruits due to the increasing in
number of plants which resulted in overall increase in
The fruit yield expressed in ton/ha significantly in-
creased with the increase of plant population in all three
pumpkin genotypes of different growth habit in the first
season. In the second season the genotypes almost showed
the same trend and this was clear in the genotype “Frosty”
and also in genotype “Pro-gold” but with less pronounced
effects. While the bush-type genotype “Frosty” did not
show any significance difference between different plant
populations in the second season.
The growth performance and yield of all genotypes
showed a consistent decline in the second season com-
pared with the first season. The performance of the geno-
types concerning fruit weight were reduced in the second
season by 33.4%, 35.2%, and 32.7% for the three geno-
types “Frosty”, “Dickinson” and “Pro-gold”, respectively.
Regarding fruit yield, the reduction was somewhat simi-
lar since the yield of three genotypes reduced by 32.1%,
37.4%, and 33.5% respectively compared with the first
The response of pumpkin genotypes to different plant
densities was genotype (growth habit) dependent. The
response was pronounced (high) in large vine type geno-
type (Dickinson and Pro-gold) compared to bush type
with compact growth (Frosty). Generally, the large vine
type genotypes gave higher yield compared to the bush
type and this may be due to the large size of its fruits.
Dickinson tends to give higher yield compared to pro-
gold (Figure 1).
3.2. The Effect of Potassium Foliar Application
To add more information regarding the interaction be-
tween different planting density and the nutrition status
of the plants, a small scale experiment was conducted by
foliar application of KNO3 to pumpkin plants grown in
different densities only in two genotypes, “frosty” (bush-
type) and “Dickinson” (large vine type) for only one year
which was the second growing season and the results are
showed in Table 2. Generally, the foliar application of
KNO3 to pumpkin genotypes did not show significant
effect on yield. However the KNO3 sprayed plants tended
to give slightly higher yield in the different planting den-
sities in both genotypes, the data also did not give clear
trend of interaction between growth habit or plant densi-
ties on pumpkin fruit weight or yield.
3.3. Analysis of Variance
Pooled analysis of variance was applied to investigate the
interaction between pumpkin genotypes and the growing
environments and the contribution of each of them to the
total variation of yield. In general, the data showed con-
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density and Variety
Copyright © 2011 SciRes. AJPS
Table 1. Fruit weight and yield of three pumpkin genotypes grown for two seasons with three different planting populations.
Fruit weight (g) Fruit Yield (ton/ha)
Genotype Plant
population/ha Season of 2010 Season of 2011 Mean Season of 2010 Season of 2011 Mean
722.65e 461.19f 591.9 3.47g 2.20d 2.84
782.87e 476.52f 629.7 5.62f 3.42d 4.52
9560 685.49e 521.29f 603.4 6.55f 4.99d 5.78
Mean 730.3c 486.3c 608.3 5.21c 3.54c 4.38
3866.7a 2860.8a 3363.8 18.47c 13.67b 16.08
3893.2a 2562.6a 3227.9 27.92b 18.38a 23.16
9560 3791.2a 2062.6bc 2926.9 36.26a 19.72a 27.99
Mean 3850.4a 2495.3a 3172.9 27.55a 13.26a 22.41
2500.0b 1712.5cd 2106.3 11.95e 8.20c 10.07
2266.7c 1527.7de 1897.2 16.25d 10.95bc 13.60
9560 1750.0d 1143.6e 1446.8 16.73d 10.92bc 13.83
Mean 2172.2b 1461.3b 1816.8 14.98c 10.02b 12.50
Values are the means of three replicates. Values followed by the same letter within a column are not significantly different at the 0.05% level of probability
according to Duncan’s multiple range test.
Table 2. Fruit weight and yield of two pumpkin genotypes grown under three different planting populations and tested for
potassium spraying (/+) effect.
Genotype Plant population/ha KNO3 (10 mM) Fruit weight (g/fruit) Fruit Yield (ton/ha)
461.19f 2.20f
4780 + 539.5f 2.58f
476.52f 3.42ef
7170 + 500.00f 3.56ef
521.29f 4.99e
9560 + 356.96f 3.42ef
2860.8ab 13.67d
4780 + 2942.2a 14.05d
2562.6bc 13.38bc
7170 + 2394.9cd 17.16c
2062.6e 19.72ab
9560 + 2203.2de 21.06a
Values are the means of three replicates. Values followed by the same letter within a column are not significantly different at the 0.05% level of probability
according to Duncan’s multiple range test.
Figure 1. Fruit weight (a) and yield (b) of three pumpkin genotypes grown for two seasons with three different planting
Dependence of Pumpkin Yield on Plant Density and Variety
siderable environment and genotype variation (Table 1)
(Figure 1). The range in fruit weight of genotypes was
between 0.7 to 3.9 kg in the first season and between 0.5
to 2.5 kg in the second season. While the range for fruit
yield was from 3.5 to 36.26 t·ha–1 in the first season and
from 2.2 to 19.72 t·ha–1 in the second season (Table 1).
When the genotypes were ranked for fruit yield and fruit
weight, there were high agreement from environment to
environment indicating the importance of genotype in
determining the yield of pumpkin (Table 1) (Figure 1).
Dickinson and Frosty usually exhibited the highest and
lowest pumpkin fruit weight and yield respectively. The
pooled analysis of variance over seasons for three geno-
types is presented in Table 3. For fruit weight, genotypic
differences described the greatest percent of the variation.
Genotypic sum of squares accounted for almost 91% of
total sum of squares (Figure 2).
Although variation due to the environment and geno-
type by environment interaction were significant but they
contribute less to the total variation (5% and 4% respec-
tively) (Table 3, Figure 2). Similar trend was observed
for fruit yield since all the three components were statis-
tically significant and represented 88%, 6%, and 6% for
genotype, environment and genotype by environment
interaction respectively (Table 3, Figure 2).
4. Discussion
Pumpkin growers are seeking different approaches to
maximize yield per unit are in order to save on land and
increase profitability. Growers need to be cognizant of
the market demands and adjust their cultural practices
accordingly to meet market expectations. The current
pumpkin market is limited by the improper size of the
fruit to most consumers.
Since competition between plants for natural resources
greatly affect yield [3] consequently it is feasible to mo-
dify size of the harvest crop to meet the requirements of
the different markets by manipulating plant density [8].
The effect of plant population on fruit weight and
yield in pumpkin genotypes were investigated in this
study. The increase of plant population from 4780 to
9560 plant/ha significantly decreased the fruit weight in
particular in large vine type genotypes which was asso-
ciated with increase in overall yield due to the increase in
number of plant per unit area. These results are in ac-
cordance with previous research in pumpkin [8,36-38,
Potassium is the most abundant inorganic cation in
plant tissues and involved in many biochemical and
physiological functions in plant such as osmoregulation
and cell extension, stomatal movement, activation of
enzymes, protein synthesis, photosynthesis and many
Table 3. Analysis of variance for yield weight (g/fruit) and
fruit yield (ton/ha) in three pumpkin genotypes grown over
two environments.
EffectSS df MS F P
(S) 20116218 1 20116218 155.4050.0000***
(g) 378322805 2 189161402 1461.3370.0000***
S*G 159316692 7965835 61.5390.0000***
(S) 228.326 1 228.326 64.9470.0000***
(g) 3281.5662 1640.783 466.7150.0000***
S*G 225.34 2 112.670 32.0490.0000***
***Significant at 0.001% level.
Figure 2. Percentages of total phenotypic variation of fruit
weight (a) and yield (b) associated with genotype, environ-
ment, and genotype by environment interaction for three
pumpkin genotypes grown over two seasons.
more [40]. Although the foliar application of potassium
to pumpkin cultivars did not reveal any significant effect
on yield, the sprayed plants tended to show slightly
higher yield in both tested genotypes overall planting
densities. The failure of potassium application to show
any significance may be due to either the low concentra-
tion of potassium foliar fertilizers or the low number of
applications. The pumpkin plants are characterized by
the huge volume of vegetative growth particularly in the
large vining types which require high inputs of foliar
application of fertilizers to be effective. Also, pumpkin
plants are known to have stiff hairs on leaf surface which
may also explain the reason of the non-significant effect
of foliar application. The slight increase in yield as a
result of potassium foliar application may be due to the
known effect of potassium in plant tolerance of biotic
and a biotic stresses [47]. In addition, this can be ex-
plained by the process of biomass allocation [48]. Ac-
cording to this process the group of non-sprayed plants
allocates a greater proportion of their biomass to the root
system compared to the sprayed plants which accumu-
lated more in their shoot system that resulted in slightly
higher fruit yield [48].
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density and Variety641
Development of pumpkin germplasm with enhanced
yield will potentially promote pumpkin cultivation and
production. This investigation found that the phenotypic
variation existing among pumpkin genotypes for yield is
primarily under genetic control. The ANOVA revealed
that the mean squares for genotypes were significant for
fruit yield. This indicates the existence of a high degree
of genetic variability in the tested plant materials that can
be exploited in a breeding programme which was also
reflected in the broad ranges observed between geno-
types for fruit yield (Table 1). The differences between
pumpkin genotypes for yield were recorded also in pre-
vious studies [49]. Plant size and growth habit differen-
ces can profoundly affect response to plant density varia-
tion [6]. Differential response of pumpkin cultivars to
increased plant density can be explained by differences
in their plant size and growth habits.
The results of this study concerning the genetic control
of pumpkin yield are supported by the moderate herita-
bility (43%) with moderately high genetic gain (44%)
that was recorded for yield by Mohanty and Mishra [50].
In addition, additive gene action has been suggested to
control the expression of yield and its components in
pumpkin [51]. These results support the feasibility of ge-
netic manipulation of yield in pumpkin. Further research
is required to investigate the influence of between rows
spacing on pumpkin yield and to confirm same results
from experiments conducted over one year (potassium
foliar application) or one location (genotype by envi-
ronment interaction).
Higher plant densities may maximize pumpkin num-
bers per unit area, but growers must realize that greater
fruit number will result in a smaller average fruit size.
Growers who choose higher population need to ensure
that all inputs are optimized to reduce potential plant-to-
plant competition. These data provide a basis for new
closer spacing recommendations for pumpkin in Egypt as
long as water and nutrients are limiting.
[1] R. Holliday “Plant Population and Crop Yield,” Nature,
Vol. 186, No. 4718, 1960, pp. 22-24.
[2] J. K. A. Bleasdale and J. A. Nelder, “Plant Population
and Crop Yield,” Nature, Vol. 186, 1960, pp. 342.
[3] J. H. M. Thornley, “Crop Yield and Planting Density,”
Annals of Botany, Vol. 52, No. 2, 1983, pp. 257-259.
[4] M. M. Pant, “Dependence of Plant Yield on Density and
Planting Pattern,” Annals of Botany, Vol. 44, No. 4, 1979,
pp. 513-516.
[5] B. B. Casper and R. B. Jackson, “Plant Competition Un-
derground,” Annual Review of Ecology and Systematics,
Vol. 28, 1997, pp. 545-570.
[6] J. K. A. Bleasdale, “Plant Growth and Crop Yield,” An-
nals of Applied Biology, Vol. 57, No. 2, 1966, pp.
173-182. doi:10.1111/j.1744-7348.1966.tb03812.x
[7] R. W. Willey and S. B. Heath, “The Quantitive Relation-
ships between Plant Population and Crop Yield,” Ad-
vances in Agronomy, Vol. 21, 1969, pp. 281-321.
[8] K. E. Cushman, D. H. Nagel, T. E. Horgan and P. D.
Gerard, “Plant Population Affects Pumpkin Yield Com-
ponents,” HortTechnology, Vol. 14, No. 3, 2004, pp.
[9] C. J. Swanton and S. F. Weise, “Integrated Weed Man-
agement in the Rational and Approach,” Weed Technol-
ogy, Vol. 5, No. 3, 1991, pp. 657-663.
[10] D. D. Buhler, “Challenges and Opportunities for Inte-
grated Weed Management,” Weed Science, Vol. 50, No. 3,
2002, 273-280.
[11] J. R. Teasdale, “Influence of Narrow Row/High Popula-
tion Corn (Zea Mays) on Weed Control and Light Trans-
mittance,” Weed Technology, Vol. 9, No. 1, 1995, pp.
[12] M. R. Speight, “The Potential of Ecosystem Management
for Pest Control. Agriculture,” Ecosystems and Environ-
ment, Vol. 10, 1983, pp. 183-199.
[13] R. H. Walker and G. A. Buchanan, “Crop Manipulation
in Integrated Weed Management Systems,” Weed Science,
Vol. 30, 1981, pp. 17-24.
[14] V. E. Rubatzky and M. Yamaguchi, “World Vegetables
Principles, Production and Nutritive Values,” 2nd Edition,
Aspen Publishers, Inc., Maryland, 1999.
[15] M. Murkovic, U. Mülleder and H. Nevnteuft, “Carote-
noid Content in Different Varieties of Pumpkin,” Journal
of Food Composition and Analysis, Vol. 15, No. 6, 2002,
pp. 633-638. doi:10.1006/jfca.2002.1052
[16] T. Hidaka and T. A. Nakatsu, “The Composition and
Vitamin a Value of the Carotenoids of Pumpkins of Dif-
ferent Colors,” Journal of Food Biochemistry, Vol. 11,
1987, pp. 59-68.
[17] Y. I. Kwon, E. Apostolidis, Y. C. Kim and K. Shetty,
“Health Benefits of Traditional Corn, Beans and Pumpkin:
In Vitro Studies for Hyperglycemia and Hypertension
Management,” Journal of Medicinal Food, Vol. 10, No. 2,
2007, pp. 266-275. doi:10.1089/jmf.2006.234
[18] I. M. Dweikat and S. R. Kostewicz, “Row Arrangement,
Plant Spacing, and Nitrogen Rate Effects on Zucchini
Squash Yield,” HortScience, Vol. 24, No. 1, 1989, pp.
[19] C. A. Powell, P. J. Stoffella and H. S. Paris, “Plant Popu-
lation Influence on Squash Yield, Sweet Potato Whitefly,
Squash Silverleaf, and Zucchini Yellow Mosaic,” Hort-
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density and Variety
Science, Vol. 28, No. 8, 1993, pp. 796-798.
[20] M. Edelstein and H. Nerson, “Genotype and Plant Den-
sity Affect Watermelon Grown for Seed Consumption,”
Hort-Science, Vol. 37, No. 6, 2002, pp. 981-983.
[21] C. E. Motsenbocker and R. A. Arancibia, “In-Row Spac-
ing Influences Triploid Watermelon Yield and Crop
Value,” HortTechnology, Vol. 12, No. 3, 2002, pp.
[22] D. S. NeSmith, “Plant Spacing Influences Watermelon
Yield and Yield Components,” HortScience, Vol. 28, No.
9, 1993, pp. 885-887.
[23] D. C. Sanders, J. D. Cure and J. R. Schultheis, “Yield
Response of Watermelon to Planting Density, Planting
Pattern, and Polyethylene Mulch,” HortScience, Vol. 34,
No. 7, 1999, pp. 1221-1223.
[24] D. Ban, S. Goreta and J. Borosic, “Plant Spacing and
Cultivar Affect Melon Growth and Yield Components,”
Scientia Horticulturae, Vol. 109, No. 3, 2006, pp. 238-
243. doi:10.1016/j.scienta.2006.04.015
[25] D. E. Knavel, “Productivity and Growth of Short-Inter-
node Muskmelon Plants at Various Spacing or Densities,”
Journal of the American Society for H or ti cu l tu ra l S ci e nc e,
Vol. 116, No. 6, 1991, pp. 926-929.
[26] F. Kultur, H. G. Harrison and J. E. Staub, “Spacing and
Genotype Affect Fruit Sugar Concentration, Yield, and
Fruit Size of Muskmelon,” HortScience, Vol. 36, No. 3,
2001, pp. 274-278.
[27] E. T. Maynard and W. D. Scott, “Plant Spacing Affects
Yield of ‘Superstar’ Muskmelon,” HortScience, Vol. 33,
No. 1, 1998, pp. 52-54.
[28] S. Mendlinger, “Effect of Increasing Plant Density and
Salinity on Yield and Fruit Quality in Muskmelon,” Sci-
entia Horticulturae, Vol. 57, No. 1-2, 1994, pp. 41-49.
[29] J. C. Roderiguez, N. L. Shaw and D. J. Cantliffe, “Influ-
ence of Plant Density on Yield and Fruit Quality of
Greenhouse-Grown Galia Muskmelons,” HortTechnology,
Vol. 1, No. 4, 2007, pp. 580-585.
[30] N. Gebologlu and N. Saglam, “The Effect of Different
Plant Spacing and Mulching Materials on the Yield and
Fruit Quality of Pickling Cucumber,” Acta Horticulturae,
Vol. 579, 2002, pp. 603-607.
[31] J. E. Staub, L. D. Knerr and H. J. Hopen, “Plant Density
and Herbicides Affect Cucumber Productivity,” Journal
of the American Society for Horticultural Science, Vol.
117, No. 1, 1992, pp. 48-53.
[32] I. E. Widders and H. C. Price, “Effects of Plant Density
on Growth and Biomass Partitioning in Pickling Cucum-
bers,” Journal of the American Society for Horticultural
Science, Vol. 114, No. 5, 1989, pp. 751-755.
[33] J. O’Sullivan, “Irrigation, Spacing and Nitrogen Effects
on Yield and Quality of Pickling Cucumber Grown for
Mechanical Harvesting,” Canadian Journal of Plant Sci-
ence, Vol. 60, No. 3, 1980, pp. 923-928.
[34] Z. Gur and L. Garte, “Influence of the Plant Density and
Sowing Date on the Yield of Pickling Cucumbers,” Acta
Horticulturae, Vol. 52, 1975, pp. 169-176.
[35] C. S. Tan, J. M. Fulton and V. W. Nuttal, “The Influence
of Soil Moisture Stress and Plant Populations on the
Yield of Pickling Cucumbers,” Scientia Horticulturae,
Vol. 21, No. 3, 1983, pp. 217-224.
[36] S. Reiners and D. I. M. Riggs, “Plant Spacing and Variety
Affect Pumpkin Yield and Fruit Size, but Supplemental
Nitrogen Does Not,” HortScience, Vol. 32, No. 6, 1997,
pp. 1037-1039.
[37] S. Reiners and D. I. M. Riggs, “Plant Population Affects
Yield and Fruit Size of Pumpkin,” HortScience, Vol. 34,
No. 6, 1999, pp. 1076-1078.
[38] R. J. Dufault and A. Korkmaz, “Influence of Plant Spac-
ing on Connecticult Field Pumpkin Size Density and
Yield,” In: J. D. McCreight, Ed., Evaluation and En-
hancement of Cucurbit Germplasm, American Society for
Horticultural Science Press, New York, 1998, pp. 51-52.
[39] C. D. Schlichting, “The Evolution of Phenotypic Plastic-
ity in Plants,” Annual Review of Ecology and Systematics,
Vol. 17, 1986, pp. 667-693.
[40] V. Romheld and E. Kirkby, “Research on Potassium in
Agriculture: Needs and Prospects,” Plant Soil, Vol. 335,
No. 1-2, 2010, pp. 155-180.
[41] H. Marschner, “Mineral Nutrition of Higher Plants,” 2nd
Edition, Academic Press, London, 1995.
[42] A. Amtmann, S. Troufflard and P. Armengaud, “The
Effect of Potassium Nutrition on Pest and Disease Resis-
tance in Plants,” Physiologia Plantarum, Vol. 133, No. 4,
2008, pp. 682-691.
[43] Statsoft Inc. “STATISTICA für Windows [Software-
system für Datenanalyse] Version 6,” 2001.
[44] S. Reiners, “Stand Establishment, Spacing and Fertiliza-
tion to Maximize Pumpkin Yield,” New England Vegeta-
ble and Fruit Conference, Manchester, 18 December
ings_ 03/pumpkin_ scholl1/stand_ establishment_ spac-
ing_ fertilization_ maximize_ pumkin_y.pdf.
[45] K. E. Cushman, T. E. Horgan, D. H. Nagel, M. Maqbool
and P. D. Gerard, “The Effect of Plant Population on
Pumpkin Yield,” Annual Report of the North Mississippi
Reseach and Extension Center, Mississippi Agricultural
and Forestry Experiment Station Information Bulletin,
Vol. 375, 2001, pp. 296-297.
[46] K. E. Cushman, T. E. Horgan, D. H. Nagel and P. D.
Gerard, “Planting Density Affects Pumpkin Size and
Weigh but Not Yield,” Annual Report of the North Mis-
sissippi Reseach and Extension Center, Mississippi Agri-
cultural and Forestry Experiment Station Information
Bulletin, Vol. 386, 2002, pp. 282-283.
[47] S. Perrenoud, “Potassium and Plant Health,” IPI-Re-
Copyright © 2011 SciRes. AJPS
Dependence of Pumpkin Yield on Plant Density and Variety
Copyright © 2011 SciRes. AJPS
search Topics No. 3, 2nd Edition, International Potash
Institute, Basel, 1990, p. 365.
[48] C. Hermans, J. R. Hammond, P. J. White and N. Ver-
bruggen, “How do Plants Respond to Nutrient Shortage
by Biomass Allocation?” Trends in Plant Science, Vol. 1,
2006, pp. 610-617. doi:10.1016/j.tplants.2006.10.007
[49] R. Karkleliene, P. Viskelis and M. Rubinskiene, “Grow-
ing, Yielding and Quality of Different Ecologically
Grown Pumpkin Cultivars,” Sodininkyste Ir Darzinin-
kyste, Vol. 27, No. 2, 2008, pp. 401-409.
[50] B. K. Mohanty and R. S. Mishra, “Variation and Genetic
Parameters of Yield and Its Components in Pumpkin,”
Indian Journal of Horticulture, Vol. 56, No. 4, 1999, pp.
[51] B. K. Mohanty, “Combining Ability for Yield and Its
Components in Pumpkin,” Indian Journal of Genetics
and Plant Breeding, Vol. 60, No. 3, 2000, pp. 33-379.