American Journal of Plant Sciences, 2013, 4, 1928-1931
http://dx.doi.org/10.4236/ajps.2013.410237 Published Online October 2013 (http://www.scirp.org/journal/ajps)
Effect of Plant Geometry on Growth and Yield of Corn in
the Rice-Corn Cropping System
Bhagirath S. Chauhan*, Jhoana L. Opeña
Weed Science, Crop and Environmental Sciences Division, International Rice Research Institute, Los Baños, Philippines.
Email: *b.chauhan@irri.org
Received July 13th, 2013; revised August 15th, 2013; accepted September 9th, 2013
Copyright © 2013 Bhagirath S. Chauhan, Jhoana L. Opeña. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
ABSTRACT
The rice-corn cropping system is increasing in Asia in response to increased demand of corn for feed. A field study was
conducted to evaluate the effect of plant geometry (row and plant to plant spacing: 50 × 20, 50 × 30, 75 × 20, and 75 ×
30 cm) on growth and yield of corn. Plant height and leaf production per plant were not influenced by the plant geome-
try. Spacing, however, influenced leaf area, aboveground shoot biomass, and yield of corn per unit area. Highest leaf
area, shoot biomass, and yield (8.2 t·ha1) were produced by plants grown at 50 × 20 cm spacing. The results of this
study suggest that narrow rows and plant to plant spacing may increase grain yield by increasing crop growth rates.
Plant geometry could be modified to improve yield of corn in the rice-corn cropping system, and thereby increase pro-
ductivity of the system.
Keywords: Row Spacing; Plant to Plant Spacing; Leaf Area; Rice-Corn Cropping System
1. Introduction
Rice (Oryza sativa L.) is the most important crop in
tropical Asia. However, the increasing scarcity of water
could lead to changes in production systems, which use
less water (for e.g., dry-seeded rice) or more crop diver-
sification [1]. Corn (Zea mays L.) is one such crop which
is more water efficient than rice and produces high yield.
The rice-corn cropping system is already gaining impor-
tance in Asia in response to the increasing demand of
corn for biofuel and feed [2]. In this cropping system,
rice in the wet season and corn in the dry season can pro-
vide high yield and it is more water-efficient than the
rice-rice cropping system. In the Philippines, corn is
grown on around 2.6 M·ha1 and around 0.12 M·ha1 is
under rice-corn cropping system [2].
Glyphosate-resistant corn is already available and
grown in the Philippines, where it is planted at 60 cm
row spacing. In other environments, narrow row spacing
has been shown to increase corn yield [3-5]. Narrow row
spacing may enhance available soil moisture to the crop
[6]. Narrow rows may also increase light interception by
the crop, for example, corn and soybean (Glycine max L.)
and therefore lead to increased crop growth [7-9]. Nar-
rowing crop rows may also result in early canopy closure
and reduced weed growth (by increased shading of weeds),
and thereby improvement in yield [10,11].
In the literature, however, data are very limited on the
effect of row spacing on corn growth and yield in the
Philippines. Therefore, a study was designed to evaluate
the effect of row spacing and plant to plant spacing on
the growth and yield of corn in the rice-corn cropping
system.
2. Materials and Methods
This study was conducted at the Experimental Station of
the International Rice Research Institute, Los Baños, La-
guna, Philippines. The soil at the experimental site had a
pH of 6.8, organic carbon of 1.2, and sand, silt, and clay
contents of 23%, 47%, and 30%, respectively. The site
was dry cultivated using a twin axle tractor before corn
planting.
There were four spacing treatments (row spacing x
plant to plant spacing within the row): 50 × 20 cm, 50 ×
30 cm, 75 × 20 cm, and 75 × 30 cm. The experiment was
arranged in a randomized complete block design with
three replications. The crop was planted by hand on Ja-
nuary 21, 2013 and immediately surface-irrigated with a
light irrigation. Phosphorus and potassium were incorpo-
*Corresponding author.
Copyright © 2013 SciRes. AJPS
Effect of Plant Geometry on Growth and Yield of Corn in the Rice-Corn Cropping System 1929
rated before crop planting at 40 kg P2O5 ha1 and 40 kg
K2O ha1, respectively. Nitrogen was applied as urea in
four splits: 40 kg·N·ha1 at 2 weeks after planting (WAP),
40 kg·N·ha1 at 4 WAP, 40 kg·N·ha1 at 6 WAP, and 40
kg·N·ha1 at 8 WAP. The size of each plot was 7.2 × 5.2
m.
Weeds were controlled by using pendimethalin at 1.0
kg ai ha1 at 1 d after planting and glyphosate (1.4 kg ai
ha1) application at 4 WAP. Herbicides were applied
with a knapsack sprayer that delivered around 320 L·ha1
of spray solution through flat fan nozzles. No measures
were taken for other pests.
Immediately after crop emergence, six consecutive
plants were tagged. Height and leaf numbers were meas-
ured for these tagged plants at 2, 4, 6, 8, and 11 WAP. In
addition, leaf area and shoot biomass (aboveground)
were measured for another six consecutive plants at 4
and 8 WAP, and converted to leaf area (cm2) m2 and
biomass (g) m2. Corn was harvested on May 14, 2013
from an area of 12 m2 (4 m × 3 m). Grain yield was con-
verted to t·ha1 at 16% moisture content.
The data of height and leaf number plant1 at different
times were fitted to a functional three-parameter sigmoid
model (SigmaPlot 10.0). The model was
()
{
}
0
1eyaxW b

= +−−

where y is the plant height or leaf number at time x, а is
the maximum height (cmplant1) or leaf number (plant1),
W0 is the time (WAP) required to reach 50% of the ma-
ximum height or leaf number, and b is the slope. The
other data (leaf area, biomass, and grain yield) were pre-
sented using standard error of mean.
3. Results and Discussion
Plant height of corn was not influenced by the spacing
(Figure 1). Although the maximum height (a) was ob-
served at 50 × 30 cm spacing, it was statistically similar
with the height at other spacing (Table 1). Similarly, the
slope was also not influenced by the spacing. The time
taken to reach 50% of the maximum height (W0) was
shortest at 50 × 20 cm (4.5 WAP) and longest at 75 × 30
cm (5.0 WAP). However, these differences were statisti-
cally non-significant.
The maximum number of leaves plant1 was observed
when the crop was planted at the narrowest spacing, that
is 50 × 20 cm, and least numbers were observed at the
widest spacing, that is 75 × 30 cm (Figure 2, Table 1).
The maximum number of leaves at different spacing
ranged from 14.6 to 17.6 leaves plant1; however, these
differences were statistically non-significant. Similarly,
the rate of leaf development (b) was also similar among
different spacing. The plants at 75 × 30 cm spacing took
2.0 WAP to reach 50% of the maximum leaf number
Weeks after planting
024681012
Plant height (cm)
0
50
100
150
200
250
300
50 x 20 cm
50 x 30 cm
75 x 20 cm
75 x 30 cm
Figure 1. Effect of plant geometry (row and plant to plant
spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on the
height of corn. A three-parameter sigmoid model was fitted
to the height data over different times.
Weeks af ter plan ting
024681012
Leav es (no. plant-1)
4
6
8
10
12
14
16
18
50 x 20 cm
50 x 30 cm
75 x 20 cm
75 x 30 cm
Figure 2. Effect of plant geometry (row and plant to plant
spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on leaf
production (number plant1) of corn. A three-parameter sig-
moid model was fitted to the data.
Table 1. Parameter estimates (± standard error) of the
three-parameter sigmoid model fitted to the plant height
and leaf number data. The fitted model was
()
{
}
0
1+e --yaxW b=, where y is the plant height or
leaf number at time x, а is the maximum height (cmplant1)
or leaf number (plant1), W0 is the time (WAP) required to
reach 50% of the maximum height or leaf number, and b is
the slope.
Spacing
(cm) a b W0 R
2
Plant height
50 × 20 240 (6) 1.51 (0.13) 4.5 (0.15) 0.99
50 × 30 241 (8) 1.46 (0.16) 4.6 (0.19) 0.99
75 × 20 235 (8) 1.64 (0.16) 4.7 (0.19) 0.99
75 × 30 237 (13) 1.59 (0.25) 5.0 (0.31) 0.99
Leaf number plant1
50 × 20 17.6 (3.2)3.82 (1.94) 2.6 (1.37) 0.95
50 × 30 15.2 (0.8)1.96 (0.57) 2.0 (0.39) 0.97
75 × 20 16.0 (0.8)2.89 (0.59) 2.2 (0.35) 0.99
75 × 30 14.6 (0.4)2.14 (0.27) 2.0 (0.18) 0.99
Copyright © 2013 SciRes. AJPS
Effect of Plant Geometry on Growth and Yield of Corn in the Rice-Corn Cropping System
1930
plant1 and the plants at 50 × 20 cm took 2.6 WAP (Ta-
ble 1). Although there was a difference of 0.6 weeks be-
tween the treatments, the difference was statistically si-
milar. The results of height and leaf numbers plant1 sug-
gest that the tested plant geometry may not influence the
development of height and leaf production in corn.
In contrast to plant height and leaf numbers, the leaf
area and shoot biomass of corn were greatly influenced
by the plant geometry. At 4 and 8 WAP, highest leaf area
was produced by plants grown at 50 × 20 cm spacing
(Table 2). The plants grown at 75 × 30 cm spacing pro-
duced lowest leaf area m2 and this was significantly
lower than the leaf area at other three spacing. Leaf area,
however, was not influenced between plants grown at 50
× 30 cm and 75 × 20 cm. A similar response was ob-
served for the aboveground biomass (Table 2). Plants
grown at 50 × 20 cm produced the highest shoot biomass
and plants grown at 75 × 30 cm produced the least shoot
biomass at 4 and 8 WAP. At 8 WAP, for example, corn
produced 1295 and 623 g·m2 of biomass when grown at
50 × 20 cm and 75 × 30 cm, respectively. At both tim-
ings (i.e., 4 and 8 WAP), the plants produced similar
biomass at 50 × 30 cm and 75 × 20 cm spacing.
Plant geometry influenced the grain yield of corn.
Highest grain yield (8.2 t·ha1) was produced by plants
grown at the narrowest spacing, that is, 50 × 20 cm (Fi-
gure 3). However, the yield at 50 cm row spacing was
not influenced (7.8 - 8.2 t·ha1) by the plant to plant
spacing. Similarly, plant to plant spacing at 75 cm rows
did not influence grain yield and it ranged from 6.1 to 6.4
t·ha1.
The results of our study suggest that narrowing row
may lead to increased leaf area and crop biomass per unit
area. Earlier studies hypothesized that narrow rows in-
creased light interception in the early growing season and
this led to increased crop growth rates and earlier can-
opy closure [3,9,12]. An earlier study reported that leaf
area increases and light transmittance to the soil surface
declines as corn plant population increases [13]. Al-
though we did not evaluate the effect of row spacing on
weed growth, various studies suggest that narrow row
spacing significantly suppresses weed growth due to ear-
lier canopy closure compared with wider rows [11,12,14,
Table 2. Effect of spacing (row and plant to plant) on leaf
area and corn biomass at 4 and 8 weeks after planting
(WAP).
Leaf area (cm2·m2) Biomass (g·m2)
Spacing (cm) 4 WAP 8 WAP 4 WAP 8 WAP
50 × 20 18947 (625) 53900 (1900) 115 (7) 1295 (104)
50 × 30 12645 (419) 38000 (1700) 72 (9) 900 (125)
75 × 20 11567 (524) 38600 (3200) 69 (6) 833 (81)
75 × 30 7249 (727) 25600 (900) 42 (6) 623 (27)
Row a nd plant to plant spacing (cm)
50 x 2050 x 3075 x 2075 x 30
Grain yield (t ha-1)
0
2
4
6
8
10
(t·ha
-1
)
Figure 3. Effect of plant geometry (row and plant to plant
spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on grain
yield of corn.
15]. Teasdale suggested the importance of the early can-
opy closure in a reduction of the critical period for weed
competition by one week [12]. Therefore, our study also
suggests that growing corn in narrow rows may have the
potential for improving weed management in reduced-
herbicide systems [12,16]. As crop cultivars differ in
their growth traits (e.g., height, leaf morphology, etc.),
more research is needed in tropical conditions to clearly
demonstrate the effect of narrow rows on growth and
yield of corn.
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