June, 2012
Journal of Resources and Ecology
J. Resour. Ecol. 2012 3 (2) 169-173
Vol.3 No.2
Report
DOI:10.5814/j.issn.1674-764x.2012.02.009
www.jorae.cn
The Temporal-Spatial Distribution of Light Intensity in Maize
and Soybean Intercropping Systems
HE Hanming, YANG Lei, ZHAO Lihua, WU Han, FAN Liming, XIE Yong, ZHU Youyong and LI Chengyun*
Key Laboratory of the Ministry of Education for Agro-Biodiversity and Pest Management, Yunnan Agricultural University, Kunming 650201, China
Abstract: Intercropping can improve field microclimates, decrease the incidence of crop diseases, and
increase crop yields, but the reasons for this remain unknown. Solar radiation is the most important
environmental influence. To understand the mechanisms of intercropping we established an experiment
consisting of three cropping patterns: a monocropping control (treatment A) and two intercropping
treatments (B: two rows of maize and two rows of soybean intercropping; C: two rows of maize and four
rows of soybean intercropping). Results show that compared to monocropping, intercropping increased
the amount of light penetrating to inferior leaves in maize plants. Light intensity reaching maize plants
at the heading stage in intercropping increased over two-fold at 30 cm above ground and 10-fold at 70
cm above ground, compared with monocropping. At the flowering to maturity stage, light intensity at 110,
160 and 210 cm above ground among maize plants was greatly increased in intercropping compared with
monocropping, by some five-fold, two-fold and 12%, respectively. Moreover, light intensity declined
more slowly at the measured heights in the intercropping system compared with monocropping. From
the 7–18th leaf, light intensity per leaf increased two-fold in intercropping compared with monocropping.
Daily light duration increased more than a mean of 5 h per day per leaf in intercropping compared with
monocropping. The biological characters of maize including thousand kernel weight, yield per plant and
area of ear leaves were all greater in intercropping than monocropping. These results suggest that, for
maize, intercropping improves light density and duration significantly and this may contribute to biomass
and yield increases.
Key words: intercropping; maize plants; light intensity; duration time; biological characters
1 Introduction
Intercropping is a traditional planting technique and is
especially common in Asia and Africa. Intercropping of
maize and soybean is known as a facilitative system, but
underlying mechanisms remain unknown, both underground
and aboveground. Intercropping can more effectively use
limited agricultural resources, including solar radiation,
fertilizers, water, gas and heat (Willey 1990; Zhu et al. 2000;
Li et al. 2009).
There is usually a positive correlation between plant dry
matter production and the amount of radiation intercepted
by crops in both sole cropping and intercropping systems
(Shibles et al. 1966; Monteith 1977; Natarajan et al.
1980; Sivakumar et al. 1984). Therefore, the temporalspatial distribution of light intensity of the crop canopy
may be the key to the production of photosynthesis and
crop yield. Some research indicates that light intensity and
the photosynthetically active radiation (PAR) intercepted
by the upper, middle and under part of the crop canopy
in glutinous and hybrid rice intercropping patterns is
above that in sole cropping pattern (Zhu et al. 2007). In
the wheat and winter pea intercrop, better light use up
to 10% was one of main causes for the advantages of
intercropping in low N conditions (Bedoussac et al. 2010).
In relay intercrops of wheat and cotton, high productivity
compared to monocultures can be fully explained by the
increase in accumulated light interception per unit of
cultivated area (Zhang et al. 2008). Maize and other short
stalk intercropping are often cultivated because of their
advantages. In maize and bean intercropping, the fraction of
radiation intercepted was higher and intercropping had more
efficient radiation harvests than sole cropping (Tsubo et al.
2001). Maize/soybean and maize/pigeon pea intercropping
Received: 2012-02-20 Accepted: 2012-05-21
Foundation: this work was supported by the National Basic Research Program (2011CB100400).
* Corresponding author: LI Chengyun. Email: [email protected].
170
Jul-28
Jul-26
Jul-24
Jul-22
Jul-20
Jul-18
Jul-16
Jul-14
Jul-12
Jul-10
Jul-8
Treatment A
Treatment B
Treatment C
Jul-6
800
700
600
500
400
300
200
100
0
Date
(b) Light intensity chang at 70cm above-ground among maize plants in
monocropping and intercropping from 14–24 Aug., 2009
Treatment A
450
400
350
300
250
200
150
100
50
0
Treatment B
Aug-24
Aug-23
Aug-22
Aug-21
Aug-20
Aug-19
Aug-18
Aug-17
Treatment C
Aug-16
A HOBO U12-012 data-logger was placed beside maize
plants. The measurement range was 1–3000 footcandles
(lumens ft -2 ). Light intensity >3000 footcandles was
recorded as the maximum value. Studies focused mostly on
the upper, middle and bottom part of maize plants, where
light intensity was usually in the measurement range. A Li6400 portable photosynthesis meter was used to measure
the photosynthetic rate of maize leaves.
Light intensity was mainly measured at two stages:
(a) Light intensity chang at 30cm above-ground among maize plants in
monocropping and intercropping from 4–28 July, 2009
Aug-15
2.2 Method
The daily mean light intensity 30 cm above ground in the
maize canopy is reported in Fig.1a. This indicates that with
increasing stem height for maize and soybean, there was
a trend of decreasing light intensity. From 4–19 July 2009
light intensity in the intercropping plot was about threefold higher than for monocropping, possibly because our
observation points were near the top of the soybean canopy,
Jul-4
Field experiments were conducted at the Yunnan
Agricultural University farm, Yunnan, China (25°07′N,
102°44′E; 1916 m a.s.l ) from 6 May 2009 to 22 October
2009. Crop varieties used in the experiment were maize
(Yunrui 88) and soybean (Nandou 12); both varieties are
widely used in Yunnan. Maize and soybean seeds were
simultaneously sown in north-south orientated rows. Three
cropping treatments were prepared. Treatment A was maize
monocropping (row distance 40 cm). Treatment B was two
maize rows (row distance 50 cm) and two soybean rows
(row distance 50 cm) intercropping (2:2). The distance from
maize to the nearest soybean row was 50 cm. Treatment C
comprised two maize rows (row distance 35 cm) and four
soybean rows (row distance 30 cm) (2:4). The distance
from maize to the nearest soybean row was 40 cm. For all
treatments the distance between maize plants was 20 cm and
distances between soybean plants was 30 cm. Experiments
were repeated three times, using a two-factor completely
randomized block design. Each unit size was 4 m x 5 m.
Full irrigation and fertilizers treatments were applied to
each cropping system.
3.1 The effect of intercropping on light intensity at 30
and 70 cm above ground during the heading stage
Aug-14
2.1 Materials
3 Results and discussion
Light intensity (footcandle)
2 Materials and methods
(i) light intensity in the maize canopy was measured at
30 and 70 cm above ground at the heading stage; and (ii)
light intensity at four positions in the maize canopy (110,
160, 210 and 260 cm above ground) was measured at the
flowering to maturity stage. The HOBO logger recorded
data every 30 min from 08:00–18:00 in the heading stage
and the flowering to maturity stage. These data were used to
calculate daily mean light intensity. The experimental field
was partially shadowed by trees, so only one replication
included three treatments was selected. Logger location was
changed daily to ensure experimental reliability. Biological
characters of maize including thousand kernel weight, yield
per plant and area of ear leaves were measured after harvest.
This research was focused on maize only, characters and
yield of soybean were ignored.
Light intensity (footcandle)
resulted in a greater land equivalent ratio (LER) and higher
economic returns as compared to monoculture at all seed
rates of soybean (Hayder et al. 2003; Dasbak et al. 2009).
A maize and peanut intercropping system helps to increase
production through the efficient utilisation of solar energy
(Awal et al. 2006).
Previous studies show that intercropping can increase
overall light use efficiency and yield. However, the light
intensity and duration reaching a maize canopy under an
intercropping or monocropping is rarely reported. It is
important to quantify the radiation energy in intercropping
compared with monocropping to analyze the benefits to
maize and any effect on yield.
The temporal-spatial distribution of light intensity
indicates the spatial change and daily change in light
intensity among crop plants. We conducted field
experiments and compared the temporal-spatial distribution
of light intensity in maize and soybean intercropping to
maize sole cropping. Our data will help us understand
how and to what extent intercropping improves the light
condition among maize plants.
Journal of Resources and Ecology Vol.3 No.2, 2012
Date
Fig.1 Light intensity at 30 and 70 cm above ground in maize
plants in monocropping and intercropping systems at the
heading stage.
171
HE Hanming, et al.: The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems
and the light reaching maize was slightly shadowed. From
20–28 July 2009, increasing plant height for soybean and
maize meant that light intensity in the intercropping and
monocropping systems decreased and then stabilized.
Fig.1b indicates that on 14–24 August 2009, very low
light intensity at 70 cm was observed in the monocropping
system, below the light compensation point (140 foot
candles). However, for intercropping, light intensity was
about 10-fold higher than for monocropping, especially
during sunny days (14–16 August, 22 August and 24
August); less difference was found for cloudy days (17–21
August, 23 August). There were no evident differences in
light intensity between treatments B and C. This shows
that light radiation was greater at 30 and 70 cm positions
for maize plant undergoing intercropping compared to
monocropping at the heading stage, especially on clear
days.
3.2 The temporal-spatial distribution of light intensity
during the flowering to maturity stage
Fig. 2a and 2b show that light intensity was high on clear
sunny days (31 August to 2 September and 7–9 September)
and was low on cloudy days (i.e. 3–6 September) in both
monocropping and intercropping C. On both clear and
cloudy days, light intensity at 110 and 160 cm height in
monocropping was always below 200 footcandles. At 110
260cm
210cm
1000
160cm
800
110cm
400
Sep-9
Sep-8
Sep-7
Sep-6
Sep-5
Sep-4
Sep-3
200
0
Sep-2
Fig. 3a and 3b illustrate that vertical patterns of light
intensity in the maize canopy were similar. This applied
to both clear and cloudy days and in monocropping and
intercropping systems. Thus, the lower the vertical height,
the weaker the light intensity. The relationship between
light intensity and vertical height was approximately linear
in monocropping, which indicates that the decrease in
light intensity as height declined was relatively rapid in
the monocropping system. However, in intercropping the
relationship between them was approximately exponential,
which may indicate that decreased light intensity with
decreased height was relatively gentle. This trend was
more obvious on clear than cloudy days. Accordingly, light
intensity reduced much slower with decreased vertical
height in intercropping than for monocropping.
(a) Light intensity on different vertical height of maize plant on clear days
600
Sep-1
3.3 The spatial distribution of light intensity in the crop
canopy
Date
Light intensity (footcandle)
1200
Aug-31
Light intensity (footcandle)
(a) The spacial distribution of light intensity among maize plant in
monocropping
cm height, light intensity was always below 100 footcandles
and lower than light compensation points. At 210 cm, light
intensity in monocropping was ~300–600 footcandles,
and light intensity in intercropping C was ~400–800
footcandles. However, at 260 cm height, the differences
of light intensity were small between intercropping and
monocropping, because the two measurement positions
were on the top of the maize canopy. Therefore, it could
be inferred that the difference between intercropping and
monocropping was mainly found at the positions under 210
cm height. Furthermore, light intensity in the maize canopy
was much higher in intercropping than in monocropping on
clear sunny days.
(b) The spacial distribution of light intensity among maize plant in
210cm
1000
160cm
800
110cm
400
200
Sep-9
Sep-8
Sep-7
Sep-6
Sep-5
Sep-4
Sep-3
0
Sep-2
R2 = 0.93, P = 0.03
100
150
200
250
300
(b) Light intensity on different vertical height of maize plant on cloudy days
600
Sep-1
R2 = 0.76, P = 0.13
260cm
1200
Aug-31
Treatment A
Treatment B
Height (cm)
Light intensity (footcandle)
Light intensity (footcandle)
intercropping (treatment C)
1400
1200
1000
800
600
400
200
0
Date
Fig. 2 The spatial distribution of light intensity among maize
plants in monocropping and intercropping C at the flowering
to maturity stage.
800
700
600
500
400
300
200
100
0
Treatment A
Treatment B
R2 = 0.81, P = 0.09
R2 = 0.93, P = 0.03
100
150
200
250
300
Height (cm)
Fig. 3 Relationship between light intensity in maize plants
and height above ground in monocropping and intercropping
systems.
172
Journal of Resources and Ecology Vol.3 No.2, 2012
Light intensity (footcandle)
th
(a) Daily mean light intersity of the 7 – 18 leaves in monocropping and
intercropping on clear days
Treatment A
900
Treatment B
800
700
600
500
400
300
200
100
0
18th 17th 16th 15th 14th 13th 12th 11th 10th 9th
8th
7th
Leaf
(b) Daily Light intensity of the 7–18th leaves in monocropping and
Leaves
12th
10th
Treatment A
18:00
16:00
14:00
12:00
8:00
10:00
18:00
16:00
14:00
8th
12:00
Time
18th
16th
14th
8:00
10:00
Light intensity (footcandle)
intercropping C on clear days
Treatment C
0–500
500–1000
1000–1500
1500–2000
Fig. 4 Daily variation in light intensity among maize plants
for different leaves in monocropping and intercropping.
3.4 Light intensity distribution of the 7–18th leaves
Light intensity data at 30, 70, 110, 160, 210 and 260 cm
above ground in both monocropping and intercropping
systems were subject to regression analysis. According
to the height of leaves, the light intensity of most maize
leaves was calculated. Fig. 4a illustrates the difference in
light intensity of the 7–18th leaves height of maize plant for
monocropping and intercropping. In intercropping, light
intensities of the 7–18th leaves positions were greater than
the light compensation point. In monocropping, only light
intensities of the 14–18th leaves positions were greater than
the light compensation point, and that of the 7–13th leaves
were below this. Ear leaves (the 12th leaf, 110 cm height)
are essential for grain production, where light intensity were
all below the light compensation point in monocropping,
but >500 footcandles in intercropping (five-fold that in
monocropping). Moreover, light intensity of the 13–17 th
leaves in intercropping was 500–800 footcandles, about
three-fold that of monocropping. The light intensity of
the 7–11th leaves in monocropping was much less than the
light compensation point in intercropping. However, the
values all reached 400 footcandles, some eight-fold that of
monocropping. Accordingly, it can be concluded that light
intensity among the maize plant of the 7–18th leaves position
in intercropping was much higher than for monocropping.
The duration of light intensity is also important for
photosynthesis. Fig. 4b shows the light intensity change
of the maize canopy in monocropping and intercropping
on a whole clear day. Light intensities of the 7–15 th
leaves in monocropping were all <500 footcandles, but
in intercropping the duration of light intensity >500
footcandles of the 9–12th leaves reached 2, 2.5, 3 and 4 h,
respectively. Furthermore, the duration of light intensity
>1000 footcandles of the 13–15th leaves, reached 2, 3 and 3 h,
respectively.
Table 1 indicates that the time of effective radiation
(viz. above the light compensation point) on the position
of most maize leaves in intercropping was longer than for
monocropping, especially from the bottom to middle part
of the maize plant. Light intensity on the position from the
7–12th leaf in monocropping was consistently below the
light compensation point. However, in intercropping the
duration of light intensity above the light compensation
point reached 5–9.5 h. The duration of light intensity
above the light compensation point from the 13–15th leaves
in monocropping was 3, 5.5 and 8 h respectively; but in
intercropping all reached 10 hours. For the 16–18th leaves
height on maize plants, the difference in the duration
of light intensity above the light compensation point
between monocropping and intercropping was not evident.
Therefore, compared to monocropping the duration of
effective radiation from the middle to top position of the
maize plant in intercropping had a definite advantage.
3.5 Comparing the biological characters of maize for
monocropping and intercropping
Ta b l e 2 i n d i c a t e s t h a t m a i z e y i e l d c h a r a c t e r s i n
intercropping, including thousand kernel weight, yield
per plant, and area of ear leaves are greater than for
maize monocropped. The thousand kernel weight showed
treatment C> treatment B > treatment A; yield per plant
showed treatment B > treatment C > treatment A; and the
area of ear leaves was B > treatment C > treatment A. From
the trial results it was seem that the biological characters of
maize were improved under an intercropping system.
Table 2 Biological characters of maize in monocropping and
intercropping.
Treatment A
Treatment B
Treatment C
Thousand kernel
weight (g)
323.8
339.2
344.9
Yield per
plant (g)
120.8
167.2
160.7
Ear leaf area
(cm2)
626
877.3
666.6
Table 1 Duration (h) of light intensity above the light compensation point for the 7–18th maize leaves height in monocropping
and intercropping.
Leaves
Monocropping
Intercropping
18th
10
10.5
17th
9.5
10.5
16th
9
10
15th
8
10
14th
5.5
10
13th
3
10
12th
0
9.5
11th
0
9.5
10th
0
9
9th
0
8.5
8th
0
7
7th
0
5
HE Hanming, et al.: The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems
4 Conclusions
Light is the most important energy source for plant
photosynthesis. Light intensity and distribution at different
heights directly affect leaf photosynthate. Our study shows
that compared with monocropping, the light intercepted in
intercropping systems differs in several aspects.
(1) Light intensity at 30 cm above ground (while the
maize was at the small bell stage) and 70 cm (near the
top of the soybean plant) for maize plants intercropped
was much higher than for monocropping. Light intensity
increased approximately two-fold and 10-fold, respectively,
on clear days.
(2) Light intensity under an intercropping system was
much higher at 110, 160 and 210 cm for maize plants and
increased about five-fold, two-fold and 12%, respectively.
The relative increase was greater on sunny days than cloudy
days. With decreasing maize plant height, light intensity
decreased more gently in the intercropping treatment than
monocropping control.
(3) From leaves 7–18th, greater light intensity reached
maize plants in intercropping than monocropping. This
increased nearly two-fold for every leaf. Light duration was
longer, by a mean of 5 h per day in intercropping compared
with monocropping.
(4) The yield components of maize including thousand
kernel weight, yield per plant and leaf area were greater in
the intercropping treatment than monocropping one.
This study suggests that light conditions for maize
were improved greatly in maize-soybean intercropping
systems, which may contribute to biomass and yield
directly. Mechanisms of intercropping are very complex,
including crop-crop interaction, crop-microbe interaction
underground, and crop-climate interaction aboveground.
Many factors lead to light interception, when intercropping
changes the crop cultivation structure and population
structure. To understand the contribution of light to the
development and growth of both maize and soybean, future
studies should measure more points to fully realize the
light distribution among maize plants. In addition, some
173
principles of light change may be quantitatively identified
by combing modeling and data, measuring biomass, disease
resistance, and yield performance under strictly controlled
conditions of light density and duration. These additional
measures and controls are necessary to understand the
effective use of light resources in intercropping systems.
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玉米净作和间作植株间光强的时空分布
何汉明，杨 磊，赵丽华，吴 晗，范黎明，谢 勇，朱有勇，李成云
农业生物多样性与病虫害控制教育部重点实验室，云南农业大学，昆明 650201
摘 要：作物多样性种植能够有效减少病虫危害，显著增加产量，但其中的机理尚不清楚。太阳辐射是最重要的影响因子
之一。本试验研究了玉米净作(A)及玉米/大豆2:2 (B，2行玉米2行大豆)和2:4 (C，2行玉米4行大豆)两种间作模式下，玉米冠层
内太阳辐射强度的时空变化。研究结果表明，多样性种植可在不同高度上对玉米植株间的受光强度和受光时间产生明显影响。
在玉米穗期，相比净作，在30cm高度上，B和C模式下光强都超过了2倍，在70cm高度上，光强超过10倍。花粒期，在110、160
和210cm位置上，相比净作，B和C模式下光强分别提高了5倍、2倍和12%，而且随着测量高度的下降，间作模式下光强下降较
为缓慢。从第7–18叶，相比净作，各叶位间作模式下光强平均增加2倍，而且日有效辐射时间平均提高了5小时。此外，玉米的
一些生物学性状，如千粒重、每株产量和穗位叶叶面积等也表现出间作B和C模式都显著高于净作。因此，间作提高了玉米的
受光强度和有效辐射时间，是改善玉米生物学性状的重要因子。
关键词: 间作；玉米；光强；持续时间；生物学性状