Effect of plant density and hand weeding on weed control and yield of the vegetable corn
ISSN 2588-1299
VJAS 2020; 3(4): 784-797
Vietnam Journal
of Agricultural
Sciences
Effect of Plant Density and Hand Weeding
on Weed Control and Yield of the Vegetable
Corn
Tran Thi Thiem, Thieu Thi Phong Thu & Nguyen Thi Loan
Faculty of Agronomy, Vietnam National University of Agriculture, Hanoi 131000, Vietnam
Abstract
Weed infestation has an adverse impact on the yield of vegetable
corn. This study, therefore, aimed to investigate the effects of plant
density and hand weeding on controlling weeds and yield of
vegetable corn. The experiments were conducted in the field
condition in a randomized complete block design with three
replications. The planting densities were 79,365 plants ha-1 (D1);
92,593 plants ha-1 (D2); 111,111 plants ha-1 (D3); and 138,889 plants
ha-1 (D4). The hand weeding treatments were no weeding (NW), hand
weeding once at 3-4 leaf stage of vegetable corn (HW1), and hand
weeding twice at 3-4 leaf and 8-9 leaf stages of vegetable corn
(HW2). The results showed that the highest planting density
combined with hand weeding was generally effective in controlling
weeds. Furthermore, the increase in planting density combined with
hand weeding significantly improved the physiological traits, which
consequently increased the cob yield. The yield was optimum at D3
combined with hand weeding once. Thus, the results suggested that
the optimum yield of vegetable corn could be obtained at a planting
density of 111,111 plants ha-1 combined with hand weeding once at
3-4 leaf stage, an increase of the cob yield by 2.01 tons ha-1.
Keywords
Planting density, hand weeding, vegetable corn, yield, weeds
Received: October 16, 2020
Accepted: March 14, 2021
Introduction
Correspondence to
Corn (Zea may L.), which is planted in 1.03 million ha producing
around 4.87 million tons in 2018, is the second most important food
crop in Vietnam after rice, (FAO, 2020). Corn is a multipurpose crop
(e.g., used as human food, animal and poultry feed, and in industrial
products) (Bibi et al., 2010). Corn can be planted and harvested
young to take advantage of its fresh, sweet, and tender ears for
vegetable purposes, called vegetable corn. Vegetable corn is a very
young cob with undeveloped seeds (Nguyen et al., 2009), which has
flavour and is rich in folate, providing 13% potassium, 14% B6
riboflavin, 17% vitamin C, and 11% fibber every four ounces (Fakir
ORCID
Tran Thi Thiem
1523
Nguyen Thi Loan
Thieu Thi Phong Thu
0301
Vietnam Journal of Agricultural Sciences
784
Tran Thi Thiem et al. (2020)
& Islam, 2008). With the increasing interest in
healthy foods worldwide, vegetable corn is a
promising food due to its quality and safety.
check. Furthermore, Kumar et al. (2017) also
showed that hand weeding resulted in the lowest
weed density and dry weight of all major weed
species, followed by other herbicide
applications, resulting in a significant increase in
rabi maize yield. Overall, these studies generally
showed that hand weeding is an effective
nonchemical approach in weed management.
There are several production constraints of
corn, i.e. unavailability of seeds of improved and
high-yielding varieties, high cost of agricultural
practices and inputs, and susceptibility to various
pathogens and insects, etc. Weed infestation is
also considered an important constraint to corn
production as weeds generally compete with the
crop for light, nutrients, water, space, and
allelopathy which reduce the yield and market
value of the crop (El-sobky & El-naggar, 2016;
Khanh et al., 2018). Worldwide, yield losses in
maize due to weeds are estimated to be
approximately 37% (Kumawat et al., 2019) and
reach as high as 90% (Dalley et al., 2006).
Although various weed control measures (e.g.,
hand weeding, mechanical weeding, and the use
of herbicides) are effective against weed
infestation in corn, each control measure has its
limitations. For instance, herbicidal control
needs repeated applications due to the re-
emergence of the weeds from the soil seed bank
which may cause herbicide resistance in the long
run with the same mode of action herbicides.
Furthermore, excessive use of herbicides allows
for the accumulation of toxicity in agricultural
products, which has negative impacts on human
health, soil, and water systems, and causes
damages to biodiversity (Al-Samarai et al.,
2018). Thus, there is a great demand for
environmentally friendly approaches to weed
management as alternatives to chemical weed
control to maximize sustainability in agricultural
production.
The frequency of hand weeding also greatly
influences maize growth and yield but may not
be economically feasible if yield largely depends
on the timing of weed, especially at the critical
stages of crop development (Abouziena et al.,
2007). Vu & Ha (2015) reported that hand
weedings at 3-4 leaf and 8-9 leaf stages of maize
significantly lower weed density and weed
biomass than single hand weeding at 3-4 leaf
stage. Abouziena et al. (2007) indicated that
there were no significant differences between
hand weeding twice (at 3 and 6 weeks after
sowing) or thrice (at 2, 4, and 6 weeks after
sowing) in controlling weeds as well as yield. In
addition, manual weeding is not always feasible
due to the lack of labour in the proper time,
higher labor cost, and unworkable condition of
the labor (Kumar et al., 2017). Therefore, it is
necessary to integrate different weed control
techniques to achieve effective and sustainable
weed control in vegetable corn production.
Planting corn at higher densities may
increase its competitive ability upon the weeds.
Higher planting densities have been used to
suppress weeds and to increase the yield of the
crop (Shapiro & Wortmann, 2006). In addition,
optimum planting density plays an important role
in efficient utilization of resources and the
competitive balance between weeds and maize
plants (El-Sobky & El-Naggar, 2016). Marín &
Weiner (2014) and Youngerman et al (2018)
found a strong negative relationship between
corn density and weed biomass at different
experimental sites when weed biomass would
decrease as corn density increased. An increase
in crop density could lead to the enhancement of
the collective shade of weeds by the crops which
suppressed weeds growth and prevented them
from reaching the crop’s initial size advantage
(Marín & Weiner, 2014). Nguyen et al. (2009)
recorded the statistically higher marketable yield
In this regard, hand weeding is still an
effective conventional weed control method, if
done properly. Dutta et al. (2016) showed that
hand weeding significantly reduced weed dry
weight and increased weed-control efficiency
(88.3%), leading to increased nutrient uptake,
thereby increasing the yield of vegetable corn by
69.9% over the weedy check. Kotru (2012) also
showed that hand weeding was as effective as
herbicide application, which increased vegetable
corn yield attributes and total yield (by 33% and
29.2%, respectively) and reduced weed biomass
and N-removal by weeds, relative to the weedy
785
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
of baby corn at the highest plant population
(167,000 plants ha-1). Moreover, Ghosh et al.
(2017) revealed that baby corn yield reached the
highest value at the density of 100,000 plants ha-
1 and slightly decreased at the density of 120,000
plants ha-1. According to Eskandarnejad et al.
(2013), with increasing the plant population from
a specific level, competition for light and
nutrients became intense and the growth of plants
was declined and crop yield would be reduced as
a result.
kg K2O ha-1 were applied. All of the P2O5 was
applied as basal during transplanting, while the N
and K2O were split equally into three
applications during transplanting, at 3-4 leaf, and
at 8-9 leaf stages of vegetable corn.
Weed species found during the experiment
were identified at harvest from the non-weeding
plot. Weed density (WD) was randomly
determined within three quadrants (0.25m2)
placed from each plot at three growth stages,
including 3-4 leaf stage, 8-9 leaf stage, and
harvest stage. The weeds within each quadrant
were oven-dried at 80oC for 48h and weighed to
determine dry mass at the harvest. Weed control
efficiency (WCE) was calculated based on the
weed dry matter recorded in each treatment at the
harvest stage of the crop using the formula
suggested by Mani et al. (1973) as follows:
Considering the above mentioned facts and
views, the experiment was conducted to study the
effect of hand weeding and planting density on
the suppression of weeds and the yield of
vegetable corn.
Materials and Methods
WCE (%) = [(Weed dry weight in the
unweeded (control) plot – Weed dry weight in the
treatment plot)/Weed dry weight in the unweeded
(control) plot] * 100.
The experiment was conducted in spring
cropping season in 2020 at the experimental
fields of the Faculty of Agronomy, Vietnam
National University of Agriculture. The seed of
vegetable corn used in the experiment was
LVN23, a good domestic variety and found more
popular in the Vietnamese market (Nguyen,
2016). The seeds were produced by the Vietnam
National Maize Research Institute.
The physiological traits such as leaf area
index (LAI) as well as dry mass of the crop were
measured at the 7-9 leaf stage, tasseling stage,
and last harvest stage using five-plant samples.
The shoots were cut from the base and oven-
dried at 80oC for 48h. The tassels and cobs were
separated and weighed separately from the rest of
the shoots.
The experiment was laid out in a
Randomized Complete Block Design (RCBD)
comprising 12 treatments with three replications.
The planting density included four levels: 79,365
plants ha-1 with 60cm x 21cm (D1); 92,593 plants
ha-1 with 60cm x 18cm (D2); 111,111 plants ha-1
with 60cm x 15cm (D3); and 138,889 plants ha-1
with 60cm x 12cm (D4). The hand weeding
treatments were: no weeding (NW), hand
weeding once at 3-4 leaf stage of vegetable corn
(HW1), and hand weeding twice at 3-4 leaf and
8-9 leaf stages of vegetable corn (HW2). The
selected planting densities were based on the
previous study of Nguyen (2016), while the hand
weeding was based on the previous study of Vu
& Ha (2015).
Leaf area index (LAI) was calculated as the
leaf area divided by the ground area, where leaf
area was calculated by the length x the maximum
width x 0.75 x the total number of leaves
(Nguyen Van Loc & Nguyen Van Minh, 2019).
At the harvest stage, the yield components such
as the number of cobs were counted by averaging
the number of harvested cobs from 10 randomly
chosen plants of each experiment plot. Cob
weight and cob yield were measured by weighing
and adding up the total weight of young cobs that
had green husk (Nguyen et al., 2009).
Statistical analysis
One seed was sown and raised in a black
plastic bag, after seven-day-old seedlings were
transplanted into the field. Hand weeding was
done by the use of a hand hoe. The fertilizer
doses of 120 kg N ha-1, 100 kg P2O5 ha-1, and 100
The data were subjected to ANOVA for the
planting density, hand weeding, interaction of
planting density and hand weeding, and
replication using IRRISTAT 5.0. The treatment
Vietnam Journal of Agricultural Sciences
786
Tran Thi Thiem et al. (2020)
mean differences were analyzed using least
significant difference (LSD) at the 5%
significance level.
density as well as the hand weeding was not
significantly different (P≤ 0.05) at the 3-4 leaf
stage. However, at the 8-9 leaf stage and harvest
stage of vegetable corn, the weed density was
significantly influenced (P≤ 0.05) by plant
density (Figure 1a). The weed density decreased
significantly with increasing plant densities from
D1 to D4. This can be explained as an initial size
advantage of crops in competition with annual
weeds which is favored by the increased degree
of size asymmetric competition caused by an
increase in the crop density (Weiner et al., 2001).
Results and Discussion
Weed species
Weed species found in the experimental
fields during the cropping period are presented
for each weed group (i.e., grass, sedge, and
broadleaf) (Suk et al., 2005). The weeds were
Eleusine india, Cynodon dactylon, Echinochloa
colona, and Leptochloa chinensis under grasses,
Cyperus rotundus under sedges, and Eclipta
alba, Rorippa indica, Portulaca oleracea,
Physalis angulata, and Alternanthera under
broadleaf (Table 1). Spring season was
characterized by incessant rain which resulted in
higher weed density, especially Cynodon
dactylon, Eleusine india, and Leptochloa
chinensis (data not shown). Vu & Ha (2015) also
reported that Cynodon dactylon, Eleusine india,
and Leptochloa chinensis were the prevalent
weeds in the maize field.
In addition, there was a significant
difference in weed density between no weeding
and hand weeding at the 8-9 leaf stage and the
last harvest stage of vegetable corn. In
comparison with non-weeding treatment, hand
weeding treatments significantly decreased weed
density (Figure 1b). Khan et al. (2012) reported
that hand weeding was the most effective way to
control the weed density in the maize field.
Furthermore, our results showed that hand
weeding twice at 3-4 leaf and 8-9 leaf stages of
vegetable corn significantly decreased the weed
density in comparison with hand weeding once at
3-4 leaf stage of vegetable corn. These results
confirmed the finding of a previous study that
hand weeding twice significantly decreased
weed density as compared with hand weeding
once (Vu & Ha, 2015).
Weed density
The effects of plant density and hand
weeding on the weed density at 3-4 leaf stage, 8-
9 leaf stage, and harvest stage of vegetable corn
are presented in Figure 1. The results showed
that the response of weed density to the plant
Table 1. Weed species in the experimental fields
No.
A.
1
Botanical name
Family
Habit
Grass
Eleusine india (L.) Gaertn
Cynodon dactylon (L.) Pers.
Echinochloa colona (L.) Link
Leptochloa chinensis (L.) Nees
Sedges
Poaceae
Poaceae
Poaceae
Poaceae
Annuals
Perennials
Annuals
2
3
4
Annuals
B.
1
Cyperus rotundus L.
Broadleaf
Cyperaceae
Perennials
C.
1
Eclipta alba (L.) Hassk
Rorippa indica (L.) Hiern
Portulaca oleracea L.
Physalis angulata L.
Alternanthera (L.) DC
Asteraceae
Brassicaceae
Portulacaceae
Solanaceae
Annuals
Annuals
Annuals
Annuals
Annuals
2
3
4
5
Amaranthaceae
787
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
200
(a)
180
160
b
b
140
120
100
80
b
ab
ab
ab
a
a
a
a
a
D1
D2
D3
D4
a
60
40
20
0
3-4 leaf stage
8-9 leaf stage
Harvest stage
200
(b)
c
180
160
140
120
100
80
b
b
a
a
a
a
a
HW
HW1
HW2
a
60
40
20
0
3-4 leaf stage
8-9 leaf stage
Harvest stage
Note: Columns with the same letter within each treatment are not significantly different at P> 0.05.
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice, respectively.
Figure 1. Effects of plant density (a) and hand weeding (b) on weed density
At the 3-4 leaf stage of vegetable corn, weed
density was not significantly influenced (P≤
0.05) by the interacting effects of plant density
and hand weeding. However, there were
significant differences in weed density among
the combination treatments at the 8-9 leaf stage
and the harvest stage of vegetable corn (Table 2).
The combination of the higher plant densities
(111,111 and 138,889 plants ha-1) and hand
weeding once or twice resulted in lower weed
density compared to the combination of the
lowest plant density (79,365 plants ha-1) and no
weeding. The results suggested that higher plant
density combined with hand weeding increased
weed suppression.
Weed dry mass
Figure 2 presents the effects of plant density
and hand weeding on weed dry weight at the
harvest stage of vegetable corn. The results
Vietnam Journal of Agricultural Sciences
788
Tran Thi Thiem et al. (2020)
showed that weed dry weight differed
significantly (P≤ 0.05) amongst the plant density
treatments as well as hand weeding treatments.
The higher plant densities had a lower weed
dry weight compared to the lowest plant
density. The results were consistent with the
work of Ahmed et al. (2014) that weed dry
weight decreased significantly with an increase
in the seedling rate of crop. In terms of hand
weeding treatment, there was a significant
difference in weed dry weight between weedy
check and hand weeding. Hand weeding once
and twice significantly decreased weed dry
weight in comparison with the weedy check.
Similar findings were presented in the study of
Vu & Ha (2015). In addition, the ANOVA
Leaf area index (LAI) of vegetable corn
Leaf area (LA) is one of the most important
growth traits as it influences the capture of solar
radiation which is important for the rapid growth
of plants (Valentinuz & Tollenaar, 2006). Thus,
plant density of corn per unit area may affect the
leaf size and its overall canopy closure which
may aid in the competitive ability of corn against
weeds. Vegetable corn grown at 92,593 plants ha-
1
and 111,111 plants ha-1 had greater LA than
138,889 plants ha-1 (data not shown). The smaller
LA at the higher plant density was possibly due
to the intra-specific competition between the
corn plants for growth resources (Murphy et al.,
1996). However, in terms of leaf area index
(LAI), analysis of the data showed that LAI
increased significantly with increasing plant
density, which was observed in all measured
growth stages of vegetable corn (Figure 3b). It
was previously shown that increasing plant
density significantly increased LAI of maize
(Nguyen et al., 2009; Timlin et al., 2014;
Lykhovyd et al., 2019; and Han et al., 2020).
The increased LAI achieved more light
interception and photosynthetic assimilation
per unit land area, thus increasing maize
biomass yield (Xu, 2018).
analysis
showed
significant
two-way
interactions between plant density and hand
weeding on weed dry weight (Table 1). Weed
dry weight was the lowest at the combination
of higher plant densities and hand weeding
twice.
Weed control efficiency (WCE)
The efficiency of treatments on the control
of weeds in terms of dry weight in comparison
with the control plot is shown in Table 2. The
adoption of different plant densities and hand
weeding controlled the weed efficiency as
evident from the weed control efficiency, which
ranged from 40.7 to 86.2%. Weed control
efficiency (WCE) increased under hand weeding
twice in comparison with hand weeding once,
regardless of plant densities. In addition, WCE
tended to increase with increasing plant density
under both hand weeding once and hand weeding
twice conditions. These results are in accordance
with the findings of Madavi et al. (2017) who
reported that higher plant density resulted in
higher WCE compared to the lower density.
Furthermore, the higher WCE was attributed to
the lower weed dry weight. A similar finding was
reported in the study of Deshpande et al. (2006).
Moreover, Gnanasoundari (2013) also suggested
that more reduction of weed dry weight by
reducing the weed density in the treatments
resulted in higher WCE.
In terms of hand weeding, there was no
significant difference in LAI between weedy
check and hand weeding plots at the 7-9 leaf
stage of vegetable corn (Figure 3a). However, at
the other measured stages, there was a significant
difference in LAI between weedy check and hand
weeding. The highest LAI was found in hand
weeding twice and the lowest LAI was in weedy
check condition, but LAI was not significantly
different between hand weeding once and hand
weeding twice as well as between hand weeding
once and weedy check.
The experimental results showed significant
differences in the interacting effects of plant
density and hand weeding on LAI at all of the
observed stages (Table 3). At the 7-9 leaf stage
of vegetable corn, the highest LAI was obtained
from the highest plant density, regardless of hand
weeding conditions. However, at both the
tasseling stage and harvest stage, the highest LAI
value was at the highest plant density combined
with hand weeding once and twice treatments
(D4HW1 and D4HW2).
789
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
120
(a)
100
80
60
40
20
0
c
b
D1
D2
D3
D4
a
a
D1
D2
D3
D4
(b)
120
c
100
80
60
40
20
0
b
NW
HW1
HW2
a
NW
HW1
HW2
Note: Columns with the same letter within each treatment are not significantly different at P> 0.05.
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice, respectively.
Figure 2. Effects of plant density (a) and hand weeding (b) on weed dry weight
At the 7-9 leaf stage, there was no significant
Dry matter weight of vegetable corn
difference in dry matter weight of vegetable corn
between no weeding and hand weeding as well
as among different plant densities (Figure 4).
However, at the tasseling stage and harvest stage,
hand weeding once and twice remarkably
The results of Figure 3 and Table 3 showed
that the dry matter weight of vegetable corn
increased over time under all treatments. The
maximum dry matter weight was observed at the
harvest stage (Figure 3 and Table 3).
Vietnam Journal of Agricultural Sciences
790
Tran Thi Thiem et al. (2020)
increased dry matter weight of vegetable corn in
comparison with no weeding. The highest dry
matter weight of vegetable corn was observed in
the hand weeding twice plots at both the above-
mentioned growth stages, while the lowest dry
matter weight of vegetable corn was found in the
no weeding plots. Similarly, in terms of plant
density, the dry matter weight of vegetable corn
increased significantly with increasing plant
density at both of these measured stages. Khan et
al. (2017) and Han et al. (2020) also reported that
increasing plant density significantly increased
shoot dry biomass of corn, which may be due to
the reduced competition from the weeds at the
higher densities.
highest dry matter weight at the tasseling stage
and harvest stage.
Yield components and yield of cobs
The results showed that there was no
significant difference in the cob weight among
plant densities, wheares there was a significant
difference in the number of cobs (Table 4a). The
maximum number of cobs was obtained at the
densities of 111,111 and 138,889 plants ha-1,
while the minimum number of cobs was
observed at the density of 79365 plants ha-1.
Therefore, increasing plant density increased the
number of cobs, which then led to an increase in
cob yield. Higher plant densities (92,593;
111,111 and 138,889 plants ha-1) resulted in
significantly higher cob yield compared to the
lower plant density (79,365 plants ha-1), but there
was an insignificant difference in cob yield
between the density of 111,111 and 138,889
plants ha-1. Similar results were observed in the
studies of Nguyen et al. (2009) and Khan et al.
(2017). This might be explained by the fact that
corn yield can be boosted with increased
The interacting effects of hand weeding and
plant density on dry matter weight of vegetable
corn are shown in Table 3. There were
significant differences in the dry matter weight
among the treatments at all of the measured
stages. Higher plant density significantly
increased the dry matter weight compared to
lower plant density, regardless of the hand
weeding. The highest plant density combined
with hand weeding once and twice had the
Table 2. Effects of plant density and hand weeding on weed density, weed dry weight, and weed control efficiency
Weed density (plant m-2)
Weed dry weight at the
harvest stage (g m-2)
Weed control
efficiency (%)
Harvest
stage
Treatment
3-4 leaf stage
8-9 leaf stage
D1
D2
D3
D4
D1
D2
D3
D4
D1
D2
D3
D4
112.5a
109.3a
97.6a
157.4b
160.9b
140.5b
136.9b
105.2a
99.8a
192.9g
180.1fg
170.8fg
156.7ef
133.5de
128.4cde
112.8bcd
96.2abc
92.9abc
83.3ab
72.1ab
60.9a
118.8h
110.9h
99.2g
94.8g
70.5f
-
NW
-
-
115.5a
116.2a
117.3a
99.2a
-
40.7
43.6
45.5
47.4
76.7
81.2
87.2
86.8
62.5ef
54.1de
49.9d
27.7c
20.9bc
12.7ab
12.5a
8.2
HW1
HW2
101.1a
89.5a
116.9a
100.1a
114.6a
112.4a
110.6a
16.2
102.5a
87.1a
101.5a
98.4a
LSD0.05
P
32.5
35.6
0.138
0.036
0.018
0.021
Note: Values followed by the same letter in each treatment column are not significantly different at the 5% level. D1, D2, D3, and
D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively. HW, HW1, and HW2: no weeding, hand
weeding once, and hand weeding twice, respectively.
791
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
Table 3. Interacting effects of plant density and hand weeding on the physiological traits of vegetable corn
LAI
Dry matter weight (g m-2 ground)
Treatment
7-9 leaf
stage
Tasseling
stage
Harvest
stage
7-9 leaf
stage
Tasseling
stage
Harvest
stage
D1
D2
D3
D4
D1
D2
D3
D4
D1
D2
D3
D4
1.07a
1.29ab
1.57b
1.95c
1.15a
1.28ab
1.52b
1.89c
1.17a
1.34ab
1.54b
1.82bc
0.31
3.48a
4.28cd
4.99fg
5.93ik
3.79ab
4.56de
5.55gh
6.35km
4.11bc
4.74ef
5.33hi
6.49m
0.45
3.56a
4.28b
5.22de
5.8f
46.6a
53.9ab
64.4bc
77.8c
48.2a
55.8ab
66.6bc
75.1c
45.8a
54.9ab
65.5bc
76.5c
13.6
278.9a
335.7bc
346.3cd
398.9de
310.5ab
355.3cd
415.1ef
496.2g
326.3abc
383.2de
434.0f
455.8a
497.6ab
563.9c
668.6de
493.8a
566.4c
634.9d
735.3f
558.5bc
635.2d
711.5ef
767.3f
64.6
NW
3.71a
4.65bc
5.66ef
6.49g
3.63a
4.84cd
5.77f
6.35g
0.53
HW1
HW2
501.8g
LSD0.05
P
40.3
0.046
0.031
0.041
0.037
0.028
0.034
Note: Values followed by the same letter in each treatment column are not significantly different at P> 0.05.
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice, respectively.
planting density, however the excessive density
can also cause yield loss due to intra-specific
competition (Shapiro & Wortmann, 2006). In
addition, Matta et al. (1990) reported that
moderately high densities may be useful to
minimize intraspecific competition between the
crop plants and wisely suppress weeds to
achieve higher grain production.
density of 111,111 plants ha-1 combined with one
and two hand weeding treatments, whereas the
minimum number of cobs was noted in the
lowest plant density combined with no weeding
treatment. There was no significant difference in
the cob weight among treatments, but there was
a significant difference in the number of cobs,
which led to the significant effect of all examined
treatments on cob yield (P≤ 0.05). The cob yield
was the lowest at the density of 79,365 plants ha-
1 combined with no weeding treatment (1.35 tons
ha-1) and the highest at the density of 111,111
plants ha-1 combined with hand weeding twice
(2.23 tons ha-1) treatments. However, there was
no significant difference in cob yield among the
density of 111,111 and 138,889 plants ha-1
combined with hand weeding once and twice
(D3HW1, D4HW1, D3HW2, and D4HW2,
respectively). The results suggested that, to
decrease the labour in manual weeding, the
vegetable corn should be planted at the density of
111,111 plant ha-1 combined with hand weeding
once, which led to an increase in the cob yield
due to the suppression of the growth of weeds.
Similar results in terms of the effects of hand
weeding were observed for the number of cobs,
cob weight, and cob yield. Hand weeding once
and twice remarkably increased cob yield in
comparison with no weeding; however, there was
no significant difference in cob yield between
hand weeding once and hand weeding twice.
Statistical analysis showed significant
effects of plant density and hand weeding on the
number of cobs and cob yield. There were also
significant two-way interactions between plant
density and hand weeding on the examined traits
(Table 4b). The maximum number of cobs was
observed in the plots with the density of 138,889
plants ha-1 combined with one and two hand
weeding treatments and was followed by the
Vietnam Journal of Agricultural Sciences
792
Tran Thi Thiem et al. (2020)
(a)
7
6
5
4
3
2
1
0
c
b
b
b
a
a
HW
HW1
HW2
a
a
a
7-9 leaf stage
Tasseling stage
Harvest stage
7
6
5
4
3
2
1
0
(b)
d
d
c
c
b
b
a
a
D1
D2
D3
D4
c
b
a
a
b
7-9 leaf stage
Tasseling stage
Harvest stage
Note: Columns with the same letter within each treatment are not significantly different at P>0.05.
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice, respectively.
Figure 3. Effects of plant density (a) and hand weeding (b) on the leaf area index of vegetable corn
indicated that increasing plant density
significantly increased green fodder yield for all
of the hybrid vegetable corns examined. In terms
of hand weeding treatment, there was a
significant difference in green biomass between
weedy check and hand weeding. Hand weeding
once and twice significantly increased green
biomass compared to the weedy check. However,
there was no significant difference in green
biomass between hand weeding once and twice.
The result of ANOVA analysis showed
Green biomass
Table 4a presents the effects of plant density
and hand weeding on the green biomass of
vegetable corn. The results showed that green
biomass differed significantly (P≤ 0.05) among
the plant density treatments as well as hand
weeding treatments. The higher plant densities
had higher green biomass compared to the lowest
plant density. Similar results were observed in
the studies of Nguyen et al. (2009) who
793
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
800
(a)
c
b
700
600
500
400
300
200
100
0
a
b
b
HW
a
HW1
HW2
a
a
a
7-9 leaf stage
Tasseling stage
Harvest stage
800
700
600
500
400
300
200
100
0
d
(b)
c
b
a
d
c
D1
D2
D3
D4
b
a
a
a a
a
7-9 leaf stage
Tasseling stage
Harvest stage
Note: Columns with the same letter within each treatment are not significantly different at P>0.05.
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice, respectively.
Figure 4. Effects of plant density (a) and hand weeding (b) on the dry matter weight of vegetable corn
combined with no weeding treatment (18.78
tons ha-1).
significant two-way interactions between plant
density and hand weeding on green biomass
(Table 4b). The maximum green biomass was
observed in the plots with the density of 138,889
plants ha-1 combined with one and two hand
weeding treatments (32.22 and 32.36 tons ha-1,
respectively), whereas the minimum green
biomass was noted in the lowest plant density
Conclusions
The results showed that increasing the plant
density combined with hand weeding once and
twice suppressed the growth of weed, which then
led to an increase in the yield of vegetable corn.
Vietnam Journal of Agricultural Sciences
794
Tran Thi Thiem et al. (2020)
Table 4a. Effects of plant density and hand weeding on yield components, cob yield, and green biomass of vegetable corn
Cob weight
(g plant-1)
Cob yield
(tons ha-1)
Number of cobs
(1000 cobs ha-1)
Green biomass (tons
ha-1)
Treatment
NW
270.19a
320.86b
320.39b
41.9
10.0a
10.2a
10.2a
1.5
1.53a
1.83b
1.99b
0.18
23.92a
25.94ab
26.42b
2.45
Hand weeding
HW1
HW2
LSD 0.05
P
0.043
0.132
9.7a
0.043
1.48a
1.72b
1.95c
1.99c
0.21
0.034
19.67a
23.07b
26.98c
31.98d
2.79
D1
D2
D3
D4
225.39a
277.16b
336.29c
376.39c
43.5
9.7a
Density
10.3a
10.8a
2.2
LSD0.05
P
0.031
0.092
0.041
0.023
Note: Values followed by the same letter in each treatment column are not significantly different at P> 0.05.
Table 4b. Interacting effects of plant density and hand weeding on yield components, cob yield, and green biomass of vegetable corn
Treatment
Hand weeding
Number of cobs
(1000 cobs ha-1)
Cob weight
(g plant-1)
Cob yield
(tons ha-1)
Green biomass (tons
ha-1)
Density
D1
196.03a
255.56bc
294.44cd
334.72de
244.44b
281.48bc
358.89ef
398.61f
235.71ab
294.45cd
355.56ef
395.83f
46.5
9.5a
9.8a
1.35a
1.47ab
1.61bc
1.69bc
1.47ab
1.71c
18.78a
22.96bc
25.67de
29.28fg
19.78ab
22.97cd
27.66ef
33.36g
20.46ab
24.27cd
27.63ef
33.22g
3.04
D2
NW
D3
9.8a
D4
9.4a
D1
9.8a
HW1
D2
10.1a
10.7a
10.2a
10.2a
11.2a
10.9a
10.2a
2.7
D3
2.01de
2.12de
1.61bc
1.99d
D4
D1
HW2
D2
D3
2.23e
D4
2.15de
LSD0.05
P
0.23
0.042
0.15
0.037
0.023
Note: Values followed by the same letter in each treatment column are not significantly different at P> 0.05;
D1, D2, D3, and D4: planting density at 79,365; 92,593; 111,111; and 138,889 plants ha-1, respectively.
HW, HW1, and HW2: no weeding, hand weeding once, and hand weeding twice , respectively.
The lower weed density and weed dry weight s
were found at the higher plant density combined
hand weeding twice treatment. Similarly, higher
plant density combined with hand weeding
resulted in higher cob yield compared to the
lowest plant density combined with no weeding
treatment. However, there was no significant
difference in cob yield among the densities of
111,111 and 138,889 plants ha-1 combined with
hand weeding once and twice. Therefore, the
results suggested that under the lack of manual
weeding labour condition, vegetable corn should
be planted at the high density of 111,111 plants
ha-1 combined with hand weeding once at 3-4
795
Effects of plant density and hand weeding on weed control and yield of the vegetable corn
India. International Journal of Pure and Applied
Bioscience. 5(3): 696-702.
leaves, which suppressed the growth of weed and
obtained the high cob yield (2.01 tons ha-1).
Han K., Liu B., Liu P. & Wang Z. (2020). The optimal plant
density of maize for dairy cow forage production.
Agronomy.
2020:
1-13.
DOI:
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